The low temperature synthesis of metal oxides by novel hydrazine method

Article abstract of DOI:10.1007/s10973-007-8515-8

The hydroxide, oxalate and citrate precursors of the metal oxides such as γ-Fe₂O₃, (MnZn)Fe₂O₄, Cu(K)Fe₂O₄, BaTiO₃, La(Sr)MnO₃, La(Sr)AlO₃, La/Gd(Ca/Ba/Sr)C

Full text of DOI:10.1007/s10973-007-8515-8

Journal of Thermal Analysis and Calorimetry, Vol. 90 (2007) 3, 627–638
THE LOW TEMPERATURE SYNTHESIS OF METAL OXIDES BY NOVEL
HYDRAZINE METHOD
*
K. S. Rane , H. Uskaikar, R. Pednekar and R. Mhalsikar
Department of Chemistry, Goa University, Goa 403206, India
The hydroxide, oxalate and citrate precursors of the metal oxides such as g-Fe
2 3 2 4 2 4 3
O , (MnZn)Fe O , Cu(K)Fe O , BaTiO ,
La(Sr)MnO , La(Sr)AlO , La/Gd(Ca/Ba/Sr)CoO , and anatase TiO on modifications with the hydrazine decompose at low temper-
3
3
3
2
atures give single phase oxides of superior properties, while the complexes without such modification require higher temperatures
for achieving the phases. The hydrazine released at lower temperatures reacts with the oxygen in the atmosphere,
–
1
N
2
H
4
+O
complexes now devoid of hydrazine. Such extra energy is not available in the case of the precursors without such modifications.
The reaction products of hydrazine oxidation provide desired partial pressure of moisture needed for the stabilization of g-Fe
Also, the nitrogen that is formed in the reaction of hydrazine with oxygen gets trapped in the lattice of TiO giving yellow color ni-
trogen doped TiO2–x photocatalyst. Thus, hydrazine method of preparation has many advantages in the preparation of metal ox-
2
®N
2 2
+2H O; DH= –625 kJ mol , and liberates enormous energy that is sufficient for the oxidative decomposition of the
2
3
O .
2
N
x
ides of superior properties.
Keywords: hydrazinate precursors, hydrazine, N-doped oxide, thermal decomposition
Introduction
better chance to obtain the desired oxides in very fine
particle size which has been realized by the chemists
over the years, but it needs furthering of research in
this area to get precursors of very low decomposition
temperature. And, we have been considering this as-
pect of synthesizing oxides of spinel, perovskite, ana-
tase structure in our laboratories [1–9] using novel
hydrazine modified precursors. Our objective in this
type of research was to prepare electric, magnetic,
sensing and photoconducting materials of submicron
size of average 100–150 nm from low temperature
thermal decomposition of metal and mixed metal
carboxylates, hydroxides. However, the modification
of these precursors by hydrazination enabled us to
further decrease the decomposition temperature re-
sulting into sub-submicron size particles of average
50–75 nm with low agglomeration as compared to
those obtained without such modifications. Since
these are easily decomposable metal complexes, it is
but natural to use the thermal analysis techniques to
assess their thermal decomposition paths. Here in the
present paper we are compiling our results of thermal
analysis of metal oxalates, citrates, hydroxides and
their hydrazinate precursors of the oxide systems such
as, g-Fe O , (MnZn)Fe O , CuFe O , Cu(K)Fe O
The recent arousal of interest in nanosize oxide mate-
rials is a challenge to the synthetic chemists as it is a
material preparation that matters a lot, that too, in the
reproducible manner. The development of nano-
structure materials with unique parameters is impossi-
ble without mastering techniques for producing such
weakly agglomerated powders with mean size of
1
0–15 nm. However, the chemists have always been
active in synthesis of submicron size materials of high
surface area active oxides that require say, for cata-
lytic applications or for further sintering them into
well dense electric, magnetic and optical materials.
But, because of their coarse nature these submicron
size particles suffer in giving properties that are grain
size controlled, such as electrical conductance. The
continued synthetic strategies adopted by the chem-
ists have enabled them to achieve materials of aver-
age particle size of 100 nm through techniques such
as sol-gel, spray-pyrolysis, pulsed laser ablation,
chemical vapor deposition, thermal decomposition
etc., whereas gas phase methods have resulted into
nanosize particles. Then, these advanced methods of
preparation of nanosize materials need metal oxide
precursors, such as metalloorganic compounds,
which are expensive and processes require stringent
conditions. Hence, it is always better to explore fur-
ther the conventional processes, such as thermal de-
composition of easily decomposable precursors of ox-
ides. Lowering of temperature of decomposition has
2
3
2
4
2
4
2
4
BaTiO3, La(Sr)MnO3, La(Sr)AlO3, La/Gd(Ca/
Ba/Sr)CoO , and anatase TiO .
3
2
Hydrazine method of preparation is a novel way
of synthesizing materials of desired structure and
properties at lower temperatures. For instance, ferrous
*
Author for correspondence: ksrane@unigoa.ac.in; ksrane@rediffmail.com
1
388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
©
2007 Akadémiai Kiadó, Budapest

RANE et al.
oxalate dihydrate, FeC
to hexagonal corundum nonmagnetic a-Fe
the hydrazinated oxalate, FeC ·2N , auto-cata-
lytically decomposes to cubic magnetic g-Fe [1–2]
and similar observations were also made for other
iron(II) carboxylates such as ferrous-fumarate/
succinate/maleate/malate/malonate [3]. Iron hydrox-
ides modified by hydrazine too showed the easy for-
2
O
4
·2H
2
O, decomposes in air
Hydroxide precursors
2
O
3
, while
Titanium hydroxide was prepared by taking titanium
iso-propoxide in iso-propanol and adding slowly to a
large quantity of water. Titanium hydroxide was also
prepared by adding ammonium hydroxide to titanium
chloride.
2
O
4
2 4
H
2
O
3
Modification of oxalate/citrate/hydroxide precursors
by hydrazine
mation of g-Fe
MgFe [6] synthesized from oxalate precursors that
modified by hydrazine showed better magnetic prop-
erties. Dielectric properties of MgFe [7] from oxa-
late hydrazinate and semiconducting properties of
g-Fe from iron hydroxides modified by hydra-
2 3
O [4]. Ni–Zn–Ferrite [5] and
2
O
4
a) Under hydrazine (UH) method: equilibration:
The oxalate and hydroxide precipitates were spread
over a Petri dish and placed in closed vessel containing
99.9% hydrazine hydrate. The hydrazine intake was
2
O
4
2
O
3
zination [8] are found to be superior as compared to
the oxide prepared from the unhydrazinated com-
pound. The titanium hydroxide and titanium oxalate
monitored by titrimetrically using KIO titrant [15].
3
b) Synthetic hydrazine (SH) method: In another
method of preparation of hydrazine modified precur-
sors, the oxalic acid and hydrazine hydrate were first
stirred well under inert nitrogen atmosphere in 3
necked retort and to the mixture a freshly prepared
metal chloride solution was rundown to precipitate
out the hydrazinated complexes.
decompose to white pigment grade anatase TiO
while their hydrazinates yield yellow color visible
light sensitive nitrogen doped TiO2–x photo-cata-
lyst [9] showing improved electrical properties [10].
In hydrothermal route for synthesizing SnO quantum
2
,
N
x
2
dots [11] the use of hydrazine hydrate is most critical
in achieving the particles in a small range of
Methods
2
.3–3.1 nm. In room temperature preparation of novel
Cu2–xSe nanotubes in organic solvents the presence of
hydrazine hydrate aids the formation [12]. A novel
low-temperature sol-gel based process in the synthe-
sis of crystalline in the Al–N–O system involves a re-
action between aluminum tri-sec-butoxide with
hydrazine hydrate [13] in the acetonitrile and chloro-
form medium. Conventional high temperature
method of preparation of CoS has been brought down
to low temperature by hydrazine assisted synthetic
process [14].
Chemical, isothermal mass loss analysis: formula
fixation
For proposing chemical formula for the oxalate, hy-
droxide, citrates and their hydrazinate complexes
chemical estimation of metals, oxalate and hydrazine
were done as per the standard methods described in
Vogel [15]. Total mass loss measurements were done
in a muffle furnace. Infrared analyses were done on
Shimadzu IR Prestige-21.
Thermal analysis
Experimental
Synthesis
Thermogravimetric analysis (TG) and differential
scanning calorimetric (DSC) analysis were preformed
on NETZSCH DSC-DTA-TG STA 409PC. The heat-
ing rate was fixed at 10°C min . The analyses were
done in the flowing air atmosphere in most of the
cases, and in few cases nitrogen gas was used.
–
1
Oxalate/citrate precursors
The oxalate precursors of spinels, MFe
2
O
M=Cu/Mn–Zn/K); perovskites, La/Gd (M )MO
M=Mn/Co/Al; M =Ca/Sr/Ba ) and BaTiO , and TiO
3
4
3
2
II
(
(
II
X-ray diffraction (XRD), SEM/TEM and XPS studies
were synthesized by standard methods. Commercial
metal chlorides and oxalic acid/citric acid were used
for the synthesis. However, in the preparation of the
The decomposed products were identified from X-ray
diffraction (XRD) studies on ITAL APD 2000 using
oxalate precursor of TiO
chloride from commercial TiO
2
a freshly prepared titanium
was used. Here the
a
CuK radiation (l=1.5418 ) and Ni filter. The dhkl
2
values obtained by XRD were matched with the
JCPDS/ICDD Card of individual oxide systems.
Scanning electron microscopic (SEM) studies were
conducted on HITACHI S-4500. Transmission elec-
tron micrographs (TEM) were recorded with
JEOL-JEM 100SX microscope, working at 100 kV
commercial titania was fused with KOH in Ni cruci-
ble and then by adding conc. HCl, potassium was re-
moved as KCl and the fresh titanium chloride that
now obtained was treated with ammonia to get tita-
nium hydroxide. The titanium hydroxide on acidify-
ing yielded a very pure titanium chloride.
6
28
J. Therm. Anal. Cal., 90, 2007

THE LOW TEMPERATURE SYNTHESIS OF METAL OXIDES BY NOVEL HYDRAZINE METHOD
accelerating voltage. X-ray photoelectron spectros-
copy (XPS) measurements were carried out over a
[26] the oxyhydroxide. A broad stretching vibration
–
mode of OH group at 3425 cm and corresponding
1
–
9
–1
bending vibration band at 1637 cm observed within
Kratas Axis Spectrometer at a vacuum of 3·10 Torr
with non-monochromatic MgK radiation.
a
a TiO
titanium alkoxide. An additional band at 1389 cm
2
sol-gel [27] occurred during the gelling of the
–
1
that had been assigned to an asymmetric bending
vibration of C–H [27] due to the presence of organic
moiety is not found in our titanium hydroxide
prepared by the hydrolysis of titanium isopropoxide,
Fig. 1a, but a broad band centered ~3340 cm due to
stretching vibration and corresponding bending
–1
vibration band at 1641 cm have appeared. On the
Nitrogen estimation, dielectric property, saturation
magnetization, electronic conductivity
The amount of nitrogen in TiO was determined using
the oxygen-nitrogen analyzer [16] (HIROBA,
EMGA, 2800). Dielectric constant of BaTiO was
2
–1
3
measured as a function of temperature in a two-probe
set up in a constant frequency of 1 KHz and that of
other hand, the hydroxide prepared from freshly
prepared titanium chloride by precipitating with
ammonia, shows, Fig. 1b, an additional band at
LaAlO
Saturation magnetization of magnetic CuFe
3
at different temperatures and frequencies.
in
2
O
4
emu/g was carried out on the instrument supplied by
M/s. Arun Electronics, Mumbai, [17] using Ni as
–1
1
~
427 cm along with very broad band centered
–1
3240 and 1631 cm . However, infrared spectra
standard. Electronic conductivity of LaCoO
was measured by Van der Pauw method [18]
3
system
recorded on the hydroxides prepared from the
titanium chloride and heat treated at different
temperatures up to 800°C, Figs 1a and b, indicate that
–
1
the band at 1427 cm vanishes and the broad band
–1
centered ~3240 cm narrows at 300°C and finally at
Results and discussion
–
00°C the ~3240 cm band shows its weak presence.
1
8
Chemical formulas
The observed percentage of oxalate, citrate,
hydrazine and total mass loss of the complexes are
compiled in the Table 1. From these values formula
for each complex is proposed and the calculated
values given in the bracket are found to match well
with observed ones. The infrared (IR) spectra of all
these complexes were recorded in the range of
a
7
00°C
6
5
00°C
00°C
400°C
3
2
00°C
00°C
100°C
–
1
4
000–400 cm and important peaks have been listed
in the Table 1. The carboxylate complexes show
rT
–
1
absorption frequencies in the range 3000–3600 cm
which may be attributed to O–H frequency (nOH) of
water, but more broadening of the peaks observed for
the hydrazinated complexes which is due to the N–H
stretching (nNH) frequencies. The carboxylate groups
have their asymmetric and symmetric stretching
frequencies, nooc asym/sym, in the region 1640–1610
4
000 3500 3000 2500 2000 1500 1000 500
Wavenumber/cm–1
b
800°C
–
1
and 1450–1375 cm , respectively. The observed
N–N stretching (nNN) frequencies in the region
700°C
600°C
5
–
980 cm indicate the presence of hydrazine, N
1
00°C
~
either as N H or as a bidentate bridging H
[
2
H
N–NH
4
,
+
400°C
2
5
2
2
1
–
2
19–21]. The NH bending vibrations at ~1600 cm
3
2
1
00°C
00°C
00°C
(
1
which could include contributions from dNH) and
–1
540 cm
[22–24] although merged in the
hydrazinate complexes of the carboxylates, band
positions in this range clearly indicate its presence in
the titanium hydroxides. The fundamental stretching
of hydroxyl (free or bonded) frequencies in the range
rT
–
1
3
600–3100 cm in the titanium hydroxide are
observed in combination with another peak
4
000 3500 3000 2500 2000 1500 1000 500
Wavenumber/cm–1
–
1630 cm due to the bending vibrations of
1
~
coordinated H O as well as Ti–OH [26]. However, a
Fig. 1 Temperature variation of FTIR of titanium hydroxide
obtained from a – titanium isopropoxide, b – titanium
chloride
2
–
peak ~1400 cm that observed has been assigned to
1
J. Therm. Anal. Cal., 90, 2007
629

RANE et al.
Table 1 Analytical and infrared data (experimental)
–1
IR peak/cm
Total mass
Proposed chemical formula
loss/%
C
%
2
O
4
/
N
%
2
4
H /
n
n
OH
NH
/
n
NN
/
ooc
n /
asym/sym dNH
d
NN
LaAl(C
LaAl(C
2
O
4
)
)
3
·10H
2
O
64.5
64.9)
64.9
64.7)
68.2
68.2)
70.9
70.8)
75.8
75.7)
74.0
73.2)
74.0
74.3)
72.5
72.8)
78.4
79.1)
76.0
75.2)
52.0
51.9)
62.7
61.2)
72.2
72.8)
76.8
76.3)
79.4
79.9)
44.1
45.0)
40.0
39.0)
66.0
65.0)
59.4
59.0)
59.9
59.8)
61.6
60.2)
64.5
64.4)
43.0
–
3200–3400 1650/1325
3200–3500 1625/1325
3200–3600 1625/1350
3200–3550 1625/1350
–
(
(43.3)
51.3
2
O
4
3
·N
2
H
4
·3H
2
O
6.7
960
960
960
–
(
(51.2)
44.0
(6.2)
11.0
2 4 3 2 4
La0.65Sr0.35Al(C O ) ·2N H
(
(43.9)
34.8
(10.6)
8.2
2 4 3 2 4 2
La0.7Sr0.3Mn(C O ) ·2N H ·15H O
(
(34.0)
–
(8.2)
–
GdCo(C
6
H
5
5
O
7
)
2
2
6
6
6
6
·2H
·4N
2
2
O
H
3400
1600/1400
(
GdCo(C
6
H
O
7
)
4
–
–
–
–
17.6
(17.7)
–
3300–3500 1700/1400
3300–3500 1700/1400
3300–3500 1750/1400
3300–3500 1750/1400
3300–3500 1750/1400
3600–3400 1680/1420
3500–3300 1680/1425
2800–3500 1600/1300
960
(
Gd0.8Ca0.2Co(C
Gd0.8Ca0.2Co(C
Gd0.8Ba0.2Co(C
Gd0.8Ba0.2Co(C
H
H
H
H
5
O
5
O
5
O
5
O
7
7
7
7
)
)
)
)
2
2
2
2
2
·10H O
(
·4N
2
H
4
17.9
(18.1)
–
980
–
(
·10H
2
O
(
·4N
H
2 4
13.6
(13.9)
–
980
(
Ba[TiO(C
Ba[TiO(C
2
2
O
4
4
)
)
2
2
]·6H
]·7N
2
O
H
59.0
(59.8)
29.1
(29.2)
59.2
(59.8)
52.1
(52.1)
43.2
(43.8)
–
(
–
O
2
4
37.0
(37.2)
–
1084
–
(
(
NH
4
)
2
)
)
TiO(C
O
2 4
)
2
·H
2
O
(
(
N
2
2
H
5
5
2
2
[TiO(C
2
O
4
4
)
)
2
]·N
2
H
4
(UH)
9.8
2200–3200 1600/1300
Very broad
980
980
–
(
(9.4)
23.5
(23.8)
–
(
N
H
[TiO(C
2
O
2
]·3N
2
H
4
(SH)
2600–3200 1700/1300
Very broad 1500
3200–3600 1400
1630
(
TiO(OH)
TiO(OH)
TiO(OH)
2
2
2
·2.5H
2
O
(
–
–
·N2H
4
(UH)
–
24.1
(24.6)
56.5
(56.6)
–
3200–4000 1400
–
(
–
–
1630
3200–4000 1400
1630
·4N
H
2 4
(SH)
–
–
(
–
–
CuFe
2
2
(C
(C
2
O
4
)
)
3
3
·8H
·3N
2
O
45.9
(45.2)
46.0
(44.3)
43.7
(43.3)
43.7
(39.3)
3500–3200 1650/1450
3500–3200 1650/1450
3500–3200 1650/1450
3500–3200 1650/1350
–
(
CuFe
2
O
4
2
H
4
·4H
2
O
16.4
(16.1)
–
980
–
(
Cu0.9
Cu0.9
K
0.1Fe
2
2
(C
(C
2
2
O
4
)
3
·9H
·5N
2
O
(
K0.1Fe
O
4
)
3
2
H
4
·9H
2
O
24.8
980
(
(23.9)
6
30
J. Therm. Anal. Cal., 90, 2007

THE LOW TEMPERATURE SYNTHESIS OF METAL OXIDES BY NOVEL HYDRAZINE METHOD
Table 1 Continued
–1
IR peak/cm
Total mass
loss/%
C
%
2
4
O /
N
%
2
4
H /
n
n
OH
NH
/
n
NN
/
Proposed chemical formula
ooc
n /
asym/sym dNH
d
NN
Mn0.65Zn0.35Fe
Mn0.65Zn0.35Fe
2
(C
(C
2
O
4
)
)
3
·8H
·3N
2
O
H
59.4
46.0
–
3500–3200 1650/1450
3500–3200 1650/1350
–
(
60.2)
61.5
62.2)
55.8
55.6)
61.8
61.5)
The numbers in parantheses mean calculated data
(45.8)
28.0
2
2
O
4
3
2
4
·5H
2
O
15.3
980
–
(
(28.3)
49.1
(15.5)
–
FeC
2
2
O
4
4
·2H
·2N
2
O
H
3500
3350
1650/1350
1650–1350
(
(48.9)
43.1
FeC
O
2
4
31.0
980
(
(42.3)
(30.8)
–
1
But the band at 1631 cm also persists at 800°C,
while in the case of the hydroxide from alkoxide the
peak at ~307°C, while its hydrazinate complex shows
an exothermic peak at ~146°C and another exotherm
between 185 and 330°C with a peak at ~270°C. The
TG mass loss curves for both the complexes between
room temperature (rT) and 330°C show two steps
decomposition, but, the hydrazine complex clearly
shows measurable two-step mass loss. The first step in
the oxalate complex is dehydration which is then
followed by decarboxylation. The first step on mass
loss in hydrazine complex is found to be due to
dehydrazination as confirmed by the absence of
hydrazine in the complex that had been isothermally
–
1
bands ~3340 and 1641 cm vanish at 500°C. These
observations suggest that the additional peak at
–
427 cm and a broad band centered ~3240 cm in
1
–1
1
the titanium hydroxide prepared by precipitating
titanium chloride with ammonia may be due to the
presence of ammonia in the precipitate.
On the basis of the results of IR and chemical
analysis (presented in Table 1) it appears that hydrazine
complexes are formed. The chemical formulas for the
GdCo complexes were difficult to ascertain, and an
adduct type [25] hydrazine complex of the citrates may
be
GdCo(C
considered
·4N
in
the
following
manner:
·4N
a
3
07
CuFe_oxalate
-
-
100
80
6
H
5
O
7
)
2
2
H
4
, Gd0.8Ca0.2Co(C
6
H
5
O
7 3
)
2
H
4
,
CuFe_oxalate-hyd
4
2
-
-
2
70
6 5 7 3 2 4
Gd0.8Ba0.2Co(C H O ) ·3N H .
DSC
146
85
Thermal analysis
332
1035
808
-60
1
511
TG-DSC traces of individual samples have been ana-
lyzed separately to record the different peak tempera-
tures and corresponding temperature ranges of mass
losses. However, for the purpose of the comparison of
the thermal paths of hydrazinate and unhydrazinate
precursors of each system, the DSC/TG traces have
been shown in one figure. Here, note that the numeri-
cal for both the temperature and DSC (mW/mg)/%
mass loss axes are arbitrary, not to the scale. The peak
temperatures shown are from the individual traces
TG
0-
1031
-
40
204
00
2
400
600 800
Temperature/°C
1000
1200
b
1
00-
Cu
Cu
K
Fe_oxalate
286
0.9 0.1
K
253
Fe_oxalate_hyd
-4
0
.9 0.1
160
80-
-
-
2
0
DSC
Spinel systems
6
0-
0-
CuFe
2 4
O system
1
99
4
TG
The TG-DSC traces of CuFe (C
2
2
O
4
)
3
·8H
·4H
2
O
O
(CuFe_oxalate)
and
CuFe (C O )
2 2 4 3
2
·3N H
4
2
2
00
400
Temperature/°C
600
800
(CuFe_oxalate_hyd) are shown in Fig. 2a. The oxalate
complex indicates a sharp endothermic peak at ~204°C
which is immediately followed by a broad intense
exothermic reaction in the range 204–332°C with a
Fig. 2 TG/DSC plots of a – copper iron oxalate/oxalate
hydrazinate, b – potassium doped copper iron oxa-
late/oxalate hydrazinate
J. Therm. Anal. Cal., 90, 2007
631

RANE et al.
decomposed separately at ~130°C. The second step in
the hydrazine complex is due to dehydration and
decarboxylation. Thus, in the temperature range
rT-330°C, the dehydration is followed by decarb-
CuFe O
2
4
oxylation in CuFe (C
2
2
O
4
)
3
·8H
(C
2
O, while in the
·3N ·4H O the
hydrazinate complex, CuFe
2
O )
2 4 3
H
2 4
2
Cu
K
Fe O
0
.9 0.1
2 4
sequence is dehydrazination-dehydration-decarb-
oxylation. At ~330°C both the complexes show almost
complete decomposition as observed in the TG trace,
beyond this temperature there is no measurable mass
change, however, DSC shows a broad exothermic up
to 1020°C and then there appears an endothermic peak
1
0
20
30
40
q/degree
50
60
70
2
Fig. 3 X-ray diffraction patterns of copper ferrite and K doped
copper ferrite obtained from oxalate hydrazinate pre-
cursors
~1030°C in both samples. The TG trace which was
showing a negligible mass loss till 1020°C suddenly
indicates a depression in the mass loss and correspond-
ing to that there appears an endotherm ~1030°C. From
the XRD studies, Fig. 3, the thermal product of
Consideration of this aspect of stabilization of the g-type
of phase was our concern [1–8] and the hydrazine
modified precursors found easily stabilize the phase, as
the desired partial pressure of moisture was provided by
the reaction products. However, in hydrazine complexes
the hydrazine liberated at lower temperature reacts with
the atmospheric oxygen liberating lot of energy [28],
2 2 4 3 2 4 2
CuFe (C O ) ·3N H ·4H O that had been isothermally
heated separately ~290°C indicated a single phase
formation, while ~330°C is required for
·8H 0 to form the spinel. Hydrazine
CuFe
CuFe
2
O
4
2
(C
2
O )
4 3
2
–
1
N
2
H
4
+O
2
®N
2
+2H
2
O; DH= –625 kJ mol
(1)
modification of the oxalate precursor enables to
prepare the spinel at low temperature.
The energy thus liberated is sufficient for oxidative
decomposition of the dehydrazinated complex and the
K-doped CuFe
O
2 4
2 2
reaction products, N +H O, provide the necessary
environment of desired partial pressure to stabilize the
g-type phase formation. The, in situ supply of heat by
coupled exothermic reaction of hydrazine with oxygen,
along with the formation of protective layer of nitrogen
and moisture surrounding each particle as a result of
reaction product is the key for stabilizing the meta stable
g-type phase. Thus, externally controlled partial
pressure of moisture during the decomposition of the
The DCS-TG traces of potassium doped oxalate and
hydrazinate complexes, Cu0.9
K
0.1Fe
2
(C
2
O
4
)
3
·9H
·9H
2
O,
O,
2
(Cu0.9K0.1_oxalate), Cu0.9K0.1Fe (C
2
O
4
)
3
·5N
2
H
4
2
(Cu0.9K0.1_oxalate_hyd) are shown in Fig. 2b. The
oxalate after showing a weak endothermic peak ~199°C
immediately indicates an intense exothermic process
with peak centered at ~253°C, while the hydrazine
complex decomposes with exothermic process with
peaks situated at ~160 and 286°C. Although the thermal
decomposition leading to ferrite formation in both the
2 4 2 4
oxalate precursors of Cu0.9K0.1Fe O and CuFe O and
in situ supply of the desired partial pressure in hydrazine
complexes lead to g-type phase. The lower saturation
magnetization values observed in the ferrite prepared
from hydrazine complex required some explanation.
The explosive nature of the reaction locally overheats
the particle as the protective layer of moisture may not
be sufficient for individual particle now acting as micro
reactors and the g-type phase of few particle may
transform into a-type.
2 4
cases is completed at ~300°C, the Cu0.9K0.1Fe O
obtained from the hydrazine complex showed single
spinel phase, Fig. 3. Magnetic characteristic such as
–1
saturation magnetization value of 28.5 emu g is
observed for Cu0.9 , while the CuFe
K0.1Fe O
2 4
2 4
O
–1
indicated a value of 21 emu g . On the other hand a
lower than 10 emu/g was observed for the oxides
obtained from oxalate precursors, suggesting that a
proper cation distribution has taken place in the spinel
oxides prepared from the hydrazine method. However,
the oxalate precursors of these oxides when
decomposed at ~320°C in a controlled atmosphere of a
(
2 4
MnZn)Fe O system
The DSC-TG traces of the oxalate show, Fig.4, an en-
dothermic peak ~218°C that followed by an intense
exothermic peak ~275°C, while the hydrazinate
complex indicates a broad exotherm in the entire
range of temperature, 140–315°C, with a peak posi-
tioned at ~185°C. The dehydration followed by
decarboxylation is the thermal path for the oxalate,
while the dehydrazination and decarboxylation are si-
multaneous processes in the case of hydrazinate com-
plex. Hydrazine complex yields the spinel phase at
known partial pressure of water vapor (N
showed higher values of 28 and 38 emu g ,
respectively, for Cu0.9 and CuFe
Controlled atmosphere of moisture is crucial in
stabilizing g-type phase as observed in FeC ·2H O [1]
which easily decomposed to g-Fe in a known partial
pressure of moisture, while in the absence of such
atmosphere the product was mainly a-Fe
2 2
/H O/Air)
–1
K0.1Fe O
2 4
2 4
O .
2 4
O
2
2 3
O
O .
2 3
6
32
J. Therm. Anal. Cal., 90, 2007

THE LOW TEMPERATURE SYNTHESIS OF METAL OXIDES BY NOVEL HYDRAZINE METHOD
6
4
2
0
-
-
-
-
-
-
-
100
80
10-
170
Fe_oxalate
Fe_oxalate-hyd
250
-100
-80
TG
2
75
Mn
Mn
Zn
Fe_oxalate
1
85
0.65 0.35
8
6
4
-
-
-
Zn Fe_oxalate-hyd
.65 0.35
0
60
-
-
-
60
40
20
TG
-40
DSC
2-
DSC
2
18
-
20
0-
3
15
210
-
1200
0
2
00
400
600 800
Temperature/°C
1000
100
200 300
Temperature/°C
400
Fig. 4 TG/DSC plots of Mn–Zn Fe-oxalate/oxalate
hydrazinate
Fig. 5 TG/DSC plots of Fe-oxalate/oxalate hydrazinate
much lower temperature of about 315°C than that of
the oxalate complex which requires more than 350°C,
the decomposition products of the oxalate at ~350°C
however, show admixture of spinel phase and
2
TiO system
Titanium hydroxide
The TG-DSC traces of titanium hydroxide,
TiO(OH) ·2.5H O,(TiOH) and its hydrazinates
2 3
unreacted Fe O . Although the spinel formation oc-
2
2
curs at lower temperatures in the case of hydrazine
method, the saturation magnetization value of 41
emu/g that observed is much lower than the value of
TiO(OH) ·1N H
4
(UH), [TiOH_hyd(UH)] and
TiO(OH) ·4N H (SH), [TiOH_hyd(SH)] are shown
2
2
2
2
4
in Fig. 6a. All show an endothermic peak ~115°C.
The endothermic process in TiO(OH) ·2.5H O is then
followed by an exothermic peak ~408°C which sug-
gest that the dehydration is followed by dehydr-
–
1
6
rite from oxalate showed mixed phases and saturation
0–80 emu g expected for the ferrite, while the fer-
2
2
–
1
magnetization of <10 emu g . The lower value may
be due to the lack of proper cation distribution and
2
also possibly some Mn ions may have oxidized to
+
3
+
TiOH_hyd(SH)
187
Mn in explosive decomposition of hydrazine pre-
cursor. However, a value of 66 emu/g , which is close
100-
TiOH_hyd.(UH)
TiOH
4
01 408
-2
-0
3
78
2 4
to 60 emu/g for nanosize Mn0.65Zn0.35Fe O [29],
1
50
DSC
8
6
4
0-
0-
0-
could be realized for the ferrite synthesized from the
oxalate precursor under controlled atmosphere of
moisture at ~350°C and then heated at 900°C at a very
–
9
–15
low partial pressure of oxygen (pO »10 –10 ) [30].
2
115
TG
g-Fe
2
O
3
system
120
116
a
-
–2
The DSC-TG traces of FeC
2
4 2
O ·2H O (Fe_oxalate),
200
400
Temperature/°C
600
800
Fig. 5, show an endothermic peak at ~210°C followed
immediately by an intense exothermic peak at
~
250°C, while FeC
thermically decomposes in the entire range of
50–200°C. The decomposition product of the oxa-
late is hexagonal corundum nonmagnetic a-Fe
1–2] and that of hydrazine complex is the mixture of
magnetic cubic spinel, g-Fe , and a-Fe . On the
2 4 2 4
O ·2N H (Fe_oxalate_hyd), exo-
5
17
4
3
-
-
-100
DSC
1
368
372
-
-
80
60
2
O
3
[
2-
1
98
Am.Ti.Oxalate
O
3
2
O
3
116
2
1
0
-
-
Hyd_Am.Ti.Oxalate (UH)
Hyd_Am.Ti.Oxalate (SH)
other hand, the hydrazine complex, spread on Petri
dish, when ignited with a burning splinter it catches
fire and a glow forms that then spreads through out
the bulk in an ordinary atmosphere, thereby, decom-
-40
-20
-0
TG
1
56
–
–
1-
2-
1
14
272
b
2 3
posing autocatalytically mostly into g-Fe O [2].
200
400
Temperature/°C
600
800
Fig. 6 TG/DSC plots of a – titanium hydroxide/hydrazinate,
b – titanium oxalate/oxalate-hydrazinate
J. Therm. Anal. Cal., 90, 2007
633

RANE et al.
oxylation. Though the dehydroxylation occurs at
400°C, the hydroxyl groups still persist in the case
of titanium hydroxide prepared by the precipitation of
titanium chloride with ammonia, while the hydroxide
prepared by the hydrolysis of titanium isopropoxide
completes its dehydroxylation below 500°C, Fig. 1.
undergoes continuous exothermic process that peaks
~
at ~505°C, while the one prepared synthetically,
[Ti_Oxalate_hyd(SH)], indicates endothermic peaks
at ~114, 156 and 270°C and then a small exothermic
peak at ~372°C that followed by an intense
exothermic peak at ~517°C. The thermal product of
The hydrazinate complex TiO(OH)
2
·1N
2
H
4
, however,
all these complexes is anatase TiO
complexes yield yellow color N-doped TiO2–xN
x
2
and the hydrazine
[9].
shows an endothermic peak ~115°C followed imme-
diately by an exothermic peak ~150°C and then there
occurs another exothermic peak ~378°C. Here the
first endothermic is found to be due to dehydra-
zination as the product that obtained by isothermally
heating the sample at ~100°C showed no presence of
hydrazine in it. The two consecutive exothermic pro-
cesses are indicative of exothermic dehydroxylation.
The endothermic peak at ~115°C that followed by
The XRD pattern of these shows an anatase type
phase as in Fig. 7. The nanosize particles are observed
in the thermal product of hydrazine complex,
whereas, agglomerated particles are found for the
decomposed product of oxalate. The TEM of these
are shown in Fig. 8. The explosive nature of the low
temperature decomposition of the hydrazine complex
may be the reason for producing nanosize particles.
exothermic peaks ~187 and 401°C in TiO(OH)
2
·
2 4
4N H
too shows that hydrazine modified hydroxide
behaves differently as compared to the hydroxide.
The thermal products in all these cases yielded well
Perovskite system
BaTiO
The DSC-TG curves of Ba[TiO(C
BaTi_oxalate) show, Fig. 9, an endothermic peak
3
crystalline anatase, TiO
Fig. 7 by a XRD pattern of anataseTiO
2
, at ~400°C as shown in
. Hydrazine
2
4 2 2
O ) ]·6H O,
2
(
method does show lower temperature decomposition
and the anatase formed by this method yields yellow
corresponding to dehydration at ~100°C followed by
an exothermic peak at ~487°C. In case of hydrazinate
2 x
color nitrogen doped TiO , TiO2–xN , [9], while the
complex,
Ba[TiO(C
2
O
4
)
2
]·7N
2
H
4
,
(BaTi_oxa-
white pigment grade oxygen deficient nonstoi-
chiometric TiO2–x was the thermal product of the tita-
nium hydroxide. Thus, the hydrazine method not only
reduces the temperature of decomposition, but also
produces yellow color N-doped visible light sensitive
late_hyd) an endothermic peak at ~98°C is followed
by a sharp exothermic peak at ~203°C and a broad
exotherm in the temperature range 210–400°C. There
occurs a small exothermic hump ~450°C. The isother-
x
TiO2–xN photocatalyst.
Titanium oxalate
The TG-DSC traces of (NH
4
)
2
[TiO(C
)
2
O
4
)
2
]·H
2
O,
(
[
(
Am.Ti.Oxalate), (N
Hyd_Am.Ti.Oxalate(UH)]
[TiO(C ]·3N
2
H
5
)
2
[TiO(C
2
O
4
2
]. N
2
H
4
(UH)
and
(SH) [Hyd_Am.Ti.
N
2
H
5
)
2
2
O
4
)
2
2
H
4
2
00nm
Oxalate(SH)] are shown in Fig. 6b. (Am.Ti.Oxalate)
decomposes giving endothermic peaks at ~114, 198,
100nm
2
Fig. 8 TEM of TiO obtained from a – oxalate hydrazinate,
2
72 and 368°C and then exothermic peak at ~500°C.
b – oxalate
The hydrazine complex prepared under hydrazine
method, [Ti_Oxalate_hyd (UH)], shows an
endothermic reaction giving peak at ~114°C and then
-
100
203
487
823
4
2
0
-
-
-
TG
TiO Anatase
2
BaTi_oxalate
BaTi_oxalate_hyd
-80
-
60
98
DSC
00
-40
1000
2
400
600
Temperature/°C
800
10
20
30
40
50
q/degree
60
70
2
Fig. 9 TG/DSC plots of BaTi oxalate/oxalate-hydrazinate
Fig. 7 XRD of anatase TiO
2
6
34
J. Therm. Anal. Cal., 90, 2007

THE LOW TEMPERATURE SYNTHESIS OF METAL OXIDES BY NOVEL HYDRAZINE METHOD
Temperature/°C
¯
La O
2 3
40
80
120
160
200
12-
-0.16
T =120°C T =115°C
c
c
1000°C
B
8
4
0
-
-
-
-
-
-
0.12
0.06
0.04
900°C
800°C
700°C
A
A-Ba_Ti_oxa_hyd
B-Ba_Ti_oxa
40
80
Temperature/°C
120
Fig. 10 Dielectric constant of A – Ba Ti oxalate hydrazinate,
B – Ba Ti oxalate
2
5
30 35 40 45 50 55 60 65 70 75 80
q/degree
Fig. 11 XRD pattern of LaAlO
3
mal studies reveal the BaTiO formation at ~450°C in
2
hydrazine complex, while the oxalate complex re-
quires a higher temperature of about 500°C to give
the perovskites. The variation of dielectric constant as
a function of temperature plots, Fig. 10, of the ferro-
3
mixed phases, (not shown here) of the perovskite and
La However, the single phase cubic
could be obtained at ~1500°C.
is a material used as a substrate for depositing
2
3
O .
3
electric BaTiO shows an increase in the value with
La0.65Sr0.35AlO
3
the increase in the temperature up to 115°C and then
decreases sharply to zero in the case of the oxide syn-
thesized by hydrazine method. The sample prepared
by oxalate route, however, shows a peak ~120°C, but
the increase, as well as the decrease is broad. The Cu-
rie temperature thus obtained is as expected for
LaAlO
3
thin films of compatible oxides of superconducting
nature and ferroelectric materials and hence the for-
mation of well dense LaAlO
hydrazine method is quite promising one, as other-
wise the ceramic technique using La and Al
3
at ~1000°C from the
O
3
2 3
O
3
BaTiO and since a sharp increase and decrease in the
2
needs very high temperature, >1400°C [31]. The vari-
ation of dielectric constant measured at different tem-
peratures and frequencies, Fig. 12 reveal that dielec-
dielectric constant observed in the oxide prepared by
hydrazine route suggests superiority of hydrazine
method.
tric constant of LaAlO
frequency up to 325°C in all frequencies studied from
KHz to 1 MHz and the value of 25 observed is close
3
has no measurable change in
LaCoO
The oxalate and oxalate hydrazinate precursors of
LaAlO and
have been synthesized
3 3 3
, LaAlO and GdCoO
1
to the expected values of 20–25 [32, 33].
La0.65Sr0.35AlO , on the other hand, shows the temper-
ature independent dielectric constant of 50 up to
3
,
La0.65Sr0.35AlO
3
,
La0.8Sr0.2CoO
3
3
La0.7Sr0.3MnO
3
and GdCoO
3
and their thermal decomposition paths have been anal-
yzed [30]. The chemical formulas of few of these pre-
cursors are shown in Table 1. The general trend is that
the hydrazine complexes show the thermal path differ-
ent from the oxalate ones, as discussed above. We are
not discussing all those here in this paper. However
some of the superior behavior of few oxides prepared
by the hydrazine method is being described here.
175°C at 1 KHz and 25 till 350°C at 1 MHz, and there
appears decrease in dielectric constant with the in-
crease in frequency 1 KHz to 1 MHz. Slightly dis-
torted
perovskites
La Sr CoO
3–d
0
.8 0.2
with
rhombohedral structure could be achieved from oxa-
late hydrazinate, La Sr Co(C O ) ·2N H ·3H O
0
.8 0.2
2
4 3
2
4
2
~1000°C, Fig. 13, while the oxalate complex gave no
single phase perovskites at this temperature. The elec-
–
1
Single phase cubic LaAlO
tained at 1000°C from LaAl(C
3
, Fig. 11, could be ob-
·N ·3H O,
tronic conductivity (S cm ) measured by Van der
Pauw method indicated that there occurs insula-
tor-metal (IM) phase change, Fig. 14, around 500 K
[34–36] in the La Sr CoO . However, an oxygen
2
O
4
)
3
2
H
4
2
while >1400°C is required to achieve the phase for
oxalate complex, as well as, for the stoichiometric
0
.8 0.2
3–d
–
2
–1
mixture of La
lighted by arrows in the XRD pattern for the sample
heated below 900°C are due to La impurity. On
the other hand, the Sr doped complex,
·2N heated at 1000°C shows
2
O
3
and Al
2
O
3
. In the figure the high-
ion conductivity of 1.995·10 (ohm cm) observed
for La Sr CoO at ~700°C is comparatively much
higher as compared to that observed by
0
.8 0.2
3
2
O
3
–
5
–1
Wiemhoefer et al. [37] of 4.6·10 (ohm cm) .
La0.65Sr0.35Al(C
2
O
4
)
3
2 4
H
J. Therm. Anal. Cal., 90, 2007
635

RANE et al.
3
Sr doped LaCoO by hydrazine method, we wanted to
1
1
1
KHz
100-
extend our preparative method in the above series of
the perovskites. And here we are describing the single
0 KHz
00 KHz
8
6
4
2
0-
0-
0-
0-
LaAlO
3
1 MHz
phase GdCoO
hydrazine method.
3 3
and Ca/Sr/Ba doped GdCoO by
3
GdCoO system
a
Chemical formulas of citrate and their hydrazinates
have been confirmed by elemental, IR and isothermal
total mass loss studies and they are as follows:
25
75 125 175 225 275 325 375 425 475 525
1
1
1
1
60-
40-
20-
00-
GdCo(C
6
H
5
O
7
)
2
6
6
6
6
·2H
2
O,
GdCo(C
2
O,
6 5 7 2 2 4
H O ) ·4N H ,
Gd0.8Ca0.2Co(C
Gd0.8Ca0.2Co(C
Gd0.8Ba0.2Co(C
Gd0.8Ba0.2Co(C
H
H
H
H
5
5
5
5
O
O
O
O
7
7
7
7
)
)
)
)
2
2
2
2
·10H
·4N
·10H
·4N
La
Sr
.65 0.35
AlO
3
0
2
4
H ,
2
O,
4
H . The TG/DSC traces of
2
8
6
4
2
0-
0-
0-
0-
all these indicate a modification in thermal path with
hydrazination, Figs 15a–d. The thermal products of
hydrazinate complexes of all these complexes give
single phase perovskites at the end of the complete
decomposition temperatures, while in the case of
citrates further heating is needed to achieve the
perovskite after the complete decomposition.
b
2
5
75 125 175 225 275 325 375 425 475 525
Temperature/°C
Fig. 12 Dielectric constant vs. temperature of a – LaAlO
3
Significance of the hydrazine method of synthesis
and b – La0.65Sr0.35AlO
3
The path of decomposition is found to be modified by
hydrazinating the hydroxide, oxalate and citrate pre-
cursors of the oxide systems studied in the present in-
vestigations. In general the hydrazine complexes de-
compose at lower temperatures than that without the
modification. The dehydration is followed by dehyd-
roxylation in the case of hydroxides and the dehydra-
tion is followed by decarboxylation in carboxylates,
while it is the dehydrazination that is followed by de-
hydration/dehydroxylation and dehydration/ decarb-
oxylation in the hydrazinated hydroxide and carboxy-
lates, respectively. The dehydrazination that takes
place at lower temperatures makes all the differences
in the thermal paths of the hydrazinated complexes. It
is the hydrazine that is released reacts with the atmo-
spheric oxygen and liberates enormous energy [28],
Eq. (1). And this energy is sufficient to oxidative de-
composition of the complex devoid of hydrazine,
while the complexes without such hydrazine modifi-
cation have no such an additional energy to decom-
pose and hence they may be decomposing at much
lower temperatures. However, it is the reaction prod-
0
20
30
40
50
60
70
2q/degree
Fig. 13 XRD of La0.8Sr0.2CoO
3
6
6
5
5
50
00
50
00
0
100 200 300 400 500 600 700 800 900
Temperature/°C
ucts of hydrazine, N
partial pressure of moisture during the decomposition
of the FeC ·2N [3] to stabilize the g-Fe , as
its importance is observed in the thermal decomposi-
tion of FeC ·2H O [1]. This is due to the fact that
FeC ·2H O decomposes in air giving mainly non-
magnetic a-Fe
2 2
+H O, that provide the required
Fig. 14 Electronic conductivity of La0.8Sr0.2CoO
3
2
O
4
2
H
4
2 3
O
A gradual IM transition from 500–700 K have
been studied [36] by systematic replacement of the
2
O
4
2
R-site in RCoO
These studies were done on the single crystals and
since we observed easy formation of the LaCoO and
3
, where R=La/Pr/Nd/Sm/Eu/Gd.
2
O
4
2
2
3
O ,
3
6
36
J. Therm. Anal. Cal., 90, 2007

THE LOW TEMPERATURE SYNTHESIS OF METAL OXIDES BY NOVEL HYDRAZINE METHOD
–
H2 O
CO / CO 2
N2
N2 / H2 O/ Air
FeC O ×2H O ¾¾ ®FeC O ¾ ¾¾ ®
Fe O ¬¾ ¾FeC O ×2H O¾¾ ¾¾ ®g-Fe O (3)
2
4
2
2
4
D
3
4
2
4
2
2
3
(
FeO®Fe O ®g-Fe O )®a-Fe O
(2)
On the other hand, the decomposition of the
·2H O in an inert atmosphere gives Fe
while in a controlled atmosphere of a known partial
2
4
2
3
2
3
And, therefore, FeC
position easily gets the desired partial pressure of
moisture from the reaction products of hydrazine, as
2
O
4
·2N
2
H
4
during its decom-
FeC
2
O
4
2
3 4
O ,
well as the thermal products of the oxalate, CO/CO
2
,
pressure of moisture the stabilization of g-Fe
place
2
O
3
takes
to stabilize the g-Fe . The energy released by the
2 3
O
hydrazine reaction with atmospheric oxygen (Eq. (1))
may be the reason for the easier low temperature de-
composition of the hydrazine complexes, but the for-
Gd-Co_citrate
Gd-Co_citrate_hyd
449
498
x
mation of yellow color nitrogen doped TiO2–xN from
-10
-8
1
00-
the hydrazine complexes of hydroxide and oxalate [9]
has to be invoked separately. No doubt the hydrazine
helps in lowering the decomposition temperature of
these complexes, but here the nitrogen that is being
formed in hydrazine break up may be getting trapped
in the lattice of the titanium oxide. An observation of
the N1s peak ~400 eV (Binding energy) in XPS stud-
TG
a
8
6
4
2
0-
0-
0-
0-
-
-
6
4
373
1
58
3
47
-2
DSC
-
-
0
6
9
131
x
ies of TiO2–xN , Fig. 16 and nitrogen content of 0.95%
–2
1
00 200 300 400 500 600 700 800
estimated using the oxygen-nitrogen analyzer [16]
further supports [9] the introduction of the nitrogen in
the TiO by hydrazine method.
Temperature/°C
2
Gd-Ca_citrate
Gd-Ca_citrate_hyd
469
1
1
1
00-
488
1
1
TG
b
-8
·10
·10
8
6
4
2
0-
0-
0-
0-
Ols
60-
Ti2p
Nls
4
0-
32-
4-
16-
3/2
6
0-
-
-
4
0
3
76
4
15
40-
40-
20-
2
1
52
DSC
2
0-
0
-
8
-
1
00 200 300 400 500 600 700 800
Temperature/°C
0-
4
08
Binding energy/eV
400
392
540 536 532 528
Binding energy/eV
468 452
Binding energy/eV
460
-
6
4
09
Gd-Ba_citrate
00-
3
51
Gd-Ba_citrate_hyd
Fig. 16 XPS of N doped TiO
2
-
4
TG
8
6
4
2
0-
0-
c
433
-2
Conclusions
1
43
0- DSC
24
• Hydrazine modified hydroxide and carboxylate
-
0
1
1
1
77 293
77
precursors of the oxide systems: g-Fe
(MnZn)Fe , CuFe , BaTiO , La(Sr)MnO
La(Sr)AlO , La/Gd(Ca/Ba/Sr)CoO
TiO decompose at low temperatures giving single
2
O
3
,
,
0-
7
4
2
O
4
2
O
4
3
3
-
–2
1
00 200 300 400 500 600 700 800
Temperature/°C
3
3
, and anatase
2
3
29
phase oxide as compared to the ones without such
modification.
Hydrazine released at low temperature during the
thermal decomposition reacts with the oxygen in
the atmosphere releasing enormous energy,
Gd-Sr-Co_citrate_hyd
Gd-Sr-Co_citrate
00-
2
95
-4
-2
TG
•
d
8
6
4
2
0-
0-
0-
0-
4
51
-
0
–1
N
2
H
4
+O
2
2 2
®N +H O; DH= –625 kJ mol
DSC
1
04
921
32
1000
that is sufficient for the oxidative decomposition of
the hydrazine devoid hydroxide and carboxylate
complexes, as compared to the simple hydroxide
and carboxylates.
9
0
-–2
9
2
00
400
600
800
1200
Temperature/°C
•
The reaction products of hydrazine reaction with
oxygen not only provide the desired partial pres-
Fig. 15 a, b, c, d TG/DSC plots of Gd
Ca,Ba,Sr)Co-citrate/citrate hydrazinate
(
J. Therm. Anal. Cal., 90, 2007
637

RANE et al.
sure of moisture that needed for stabilizing the
g-Fe , but also help to incorporate the nitrogen in
the lattice of TiO to yield yellow color N-doped
photocatalayst.
14 J. H. Zhan, Y. Xie, X. G. Yang, W. X. Zhang and
Y. T. Qian, J. Solid State Chem., 146 (1999) 36.
5 I. A. Vogel, A Text Book of Quantitative Inorganic
Analysis, Longman, UK 1978.
2
O
3
1
1
2
TiO2–xN
x
6 S. Yin, H. Yamaki, M. Komatsu, Q. Zhang, J. Wang,
Q. Tang, F. Saito and T. Sato, J. Mater. Chem.,
1
3 (2003) 2996.
Acknowledgements
1
1
7 S. D. Likhite, C. Radhakrishnamurthy and
P. W. Sahasrabudhe, Rev. Sci. Instrum., 36 (1965) 1558.
8 L. G. Van der Pauw, Philips Research Reports,
KSR thanks German Academic Exchange Service (DAAD)
for awarding NETZSCH DSC-TG STA 409PC equipment un-
der its Global Equipment Grants program (DAAD-Sachmittel-
programm/Gerätespendenprogramm; ref.432a@daad.de) and
Department of Science and Technology (DST), New Delhi,
for supporting further to add NETZSCH DTA carrier to the
equipment under major project grant (Dr. Srinivasan/KSR).
Thanks are also due to University Grants Commission (UGC),
New Delhi, for financial assistance to RM. KSR also acknowl-
edges the financial support of UGC and DST to the Depart-
ment of Chemistry, Goa University, under the UGC-Special
Assistance Program and DST-FIST program.
13 (1958) 1; A. A. Ramadan, R. D. Gould nad A. Ashour,
Thin Solid Films, 239 (1994) 272.
1
2
2
2
2
2
9 A. Braibanti, F. Dallavalle, M. A. Pellinghelli and
E. Leporati, Inorg. Chem., 7 (1968) 1430.
0 A. Yasodhai and S. Govindarajan, J. Therm. Anal. Cal.,
6
7 (2002) 679.
1 L. Sacconi and A. Sabatini, J. Inorg. Nucl. Chem.,
5 (1963) 1389.
2
2 A. Earnshaw, L. F. Larkworthy and K.S. Patel, Z. Anorg.
Allg. Chem., 334 (1964) 163.
3 W. G. Patterson and M. Onyszchuk, Can. J. Chem.,
41 (1963) 1872.
4 J. N. Kim, M. A. Sriram, P. H. McMichael, P. N. Kumta,
B. L. Phillips and S. H. Risbud, J. Phys. Chem. B.,
References
101 (1997) 4689.
1
2
3
4
5
6
7
8
9
K. S. Rane, A. K. Nikumbh and A. J. Mukhedkar,
J. Mater. Sci., 16 (1981) 2387.
25 M. S. Bains and D. C. Bradley, Can. J. Chem.,
40 (1962) 1350.
V. Borker, K. S. Rane andV. N. Kamat Dalal, J. Mater.
Sci. Mater. Electr., 4 (1993) 241.
K. S. Rane and V. M. S. Verenkar, Bull. Mater. Sci.,
26 Y. Gao, Y. Masuda, Z. Peng, T. Yonezawa and
K. Koumoto, J. Mater. Chem., 13 (2003) 608.
27 T. Lopez, J. A. Moreno, R. Gomez, X. Bokhimi,
J. A. Wang, H. Yee-Madeira, G. Pecchi and P. Reyes,
J. Mater. Chem., 12 (2002) 714.
24 (2001) 39.
K. S. Rane, V. M. S. Verenkar and P. Y. Sawant, Bull.
Mater. Sci., 24 (2001) 331.
28 E. W. Schmidt, Hydrazine and its Derivatives-Preparation,
Properties and Applications, Wiley Interscience
New York 1984.
V. Moye, K. S. Rane and V. N. Kamat Dalal, J. Mater.
Sci. Mater. Electr., 1 (1990) 212.
K. S. Rane, V. M. S. Verenkar and P. Y. Sawant, J. Mater.
Sci. Mater. Electr., 10 (1999) 133.
29 C. Rath, N. C. Mishra, S. Anand, R. P. Das, K. K. Sahu,
U. Chandan and H. C. Verma, Appearance of superpara-
K. S. Rane, V. M. S. Verenkar and P. Y. Sawant, Mater.
Sci., 24 (2001) 323.
2 4
magnetism on heating nanosize Mn0.65Zn0.35Fe O ’,
(adsabs.harvard.edu/abs/ 2000ApPhL.. 76..475R), Applied
Phys. Letters, 76 (2000) 475.
K. S. Rane, V. M. S. Verenkar, R. M. Pednekar and
P. Y. Sawant, J. Mater. Sci. Mater. Electr., 10 (1999) 121.
K. S. Rane, R. Mhalsiker, S. Yin, T. Sato, K. Cho,
E. Dunbar and P. Biswas, J. Solid State Chem.,
30 R. M. Pednekar, ‘Synthesis and characterization of metal
and mixed metal oxides of spinel and perovskite
structure’, Ph.D. Thesis Goa Univeristy, Goa, India 2006.
31 G. Y. Sung, K. Y. Kong and S.-C. Park, J. Am. Ceram.
Soc., 74 (1991) 437.
1
79 (2006) 3033.
0 R. Mhalsikar, R. Pednekar and K. S. Rane, Electrical
Characteristics of TiO synthesized from different
1
32 B.-E. Park and H. Ishiwara, Appl. Phys. Lett., 82 (2003) 1197.
33 P. Delugas, V. Fiorentini and A. Filippeti, Phys. Rev. B.,
71 (2005) 134302.
2
precursors, Inorganic Materials: Recent Advances.
Eds: D. Bahadur, S. Vitta, Om Prakash, Narosa
Publishing House, New Delhi, India (Paper presented at
the International Symposium in Inorganic Chemistry,
IIT-Bombay, Mumbai, India, Dec. 11–13 2002)
pp. 469–471.
34 S. Yamaguchi, Y. Okimoto and Y. Tokura, Phys. Rev. B.,
55 (1997) R8666.
35 S. Yamaguchi, Y. Okimoto, H. Taniguchi and Y. Tokura,
Phys. Rev. B., 53 (1996) R2926.
1
1
1
1 H. Zhu, D. Yang, G. Yu, H. Zhang and K. Yao,
Nanotechnology, 17 (2006) 2386.
36 S. Yamaguchi, Y. Okimoto and Y. Tokura, Phys. Rev. B.,
54 (1996) R11 022.
2 Y. Jiang, Y. Wu, B. Xie, S. Zhang and Y. Qian,
Nanotechnology, 15 (2004) 283.
37 W. Zipprich, S. Waschilewski, F. Rocholl and
H. D. Wiemhoefer, Solid State Ionics, 101–103 (1997) 1015.
3 J. Y. Kim, M. A. Sriram, P. H. McMichael, P. N. Kumta,
B. L. Phillips and S.H. Risbud, J. Phys. Chem. B,
DOI: 10.1007/s10973-007-8515-8
101 (1997) 4689.
6
38
J. Therm. Anal. Cal., 90, 2007