Phase transformations in the TiO2-NiO system

Article abstract of DOI:10.1134/S0020168512050202

The anatase-rutile phase transition in fine-particle TiO₂-NiO oxides has been studied using physicochemical characterization techniques (X-ray diffraction, differential thermal analysis, and mass spectrometry). The results demonstrate that NiO

Full text of DOI:10.1134/S0020168512050202

ISSN 0020ꢀ1685, Inorganic Materials, 2012, Vol. 48, No. 5, pp. 488–493. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © V.V. Viktorov, E.A. Belaya, A.S. Serikov, 2012, published in Neorganicheskie Materialy, 2012, Vol. 48, No. 5, pp. 570–575.
Phase Transformations in the TiO2–NiO System
V. V. Viktorova, E. A. Belayab, and A. S. Serikova
a Chelyabinsk State Pedagogical University, pr. Lenina 69, Chelyabinsk, 454080 Russia
eꢀmail: viktorovvv.cspu@mail.ru
b Chelyabinsk State University, ul. Br. Kashirinykh 129, Chelyabinsk, 454001 Russia
eꢀmail: belenkaya79@list.ru
Received March 21, 2011; in final form, December 10, 2011
Abstract—The anatase–rutile phase transition in fineꢀparticle TiO2–NiO oxides has been studied using
physicochemical characterization techniques (Xꢀray diffraction, differential thermal analysis, and mass
spectrometry). The results demonstrate that NiO additions considerably increase the rate of the anatase–
rutile polymorphic transformation. Nickel titanate formation depends on the procedures used to prepare
both titanium dioxide and nickel oxide. In the temperature range 700–850°C, the anatase to rutile phase
transition prevents nickel titanate formation.
DOI: 10.1134/S0020168512050202
INTRODUCTION
of interest to examine the effect of startingꢀmixture
history on phase formation in fineꢀparticle TiO2–NiO
oxides.
The objectives of this work were to study the effect
of NiO on the anatase to rutile phase transition in fineꢀ
particle TiO2–NiО oxides and the effect of the history
of starting oxides on this phase transition.
Fineꢀparticle titanium(IV) oxide, a chemically staꢀ
ble, nontoxic, relatively inexpensive material, finds
wide application in various areas of science and techꢀ
nology, in particular, in the production of pigments,
optical materials, photocatalysts, and dielectric
ceramics [1–3].
Titanium(IV) oxide exists in three polymorphs—
anatase, rutile, and brookite—and forms a number of
Magneli phases. Brookite is of no practical imporꢀ
tance. Anatase has a tetragonal structure and is a metaꢀ
stable phase of titanium dioxide. Rutile also has a tetꢀ
ragonal structure, but it differs from that of anatase [4].
EXPERIMENTAL
The starting chemicals used were hydrolytic titaꢀ
nium dioxide (HTD), nonpigment titanium dioxide
(anatase), and NiO.
Nickel(II) oxide undergoes antiferromagnetic
ordering and is a magnetic semiconductor of great
practical importance. It is used in the production of
ferrite material; as a pigment for glass, glazes, and
ceramics; and as a catalyst for many chemical proꢀ
cesses [5].
In the TiO2–NiO system, a number of nickel titanꢀ
ates may form, depending on NiO content, temperaꢀ
ture, and reaction time: NiTiO3, Ni2TiO4 and highꢀ
Anatase was prepared by two procedures. In proceꢀ
dure I, HTD was calcined at 600°С for 2 h. HTD was
prepared as described in detail elsewhere [1], through
thermal hydrolysis of Ti(IV) sulfate solutions. The
process was run in the presence of anatase nuclei,
which acted as centers for the formation of primary
HTD particles during the hydrolysis. In procedure II,
we hydrolyzed TiCl4 and titanium tetrabutoxide
(TTB), and the resultant precipitate was calcined at
600°С to give anatase. The titanium dioxide thus preꢀ
pared was analyzed for impurities on a PGS 2 specꢀ
trograph.
temperature (t > 1400°C) nonstoichiometric spinels
with the general formula Ni2 – 2xTi1 – xO4, where
x =
0.03–0.75 [6].
Nickel oxide was prepared through thermolysis of
analyticalꢀgrade basic nickel carbonate and nickel
nitrate hexahydrate. These salts were chosen as preꢀ
cursors because they differ little in decomposition
NiTiO3 can be synthesized by a variety of techꢀ
niques using organotitanium precursors, e.g., oxalate
complexes [7] or titanium(IV) butoxide [8–10].
Recent work [11] has shown that the addition of
25 wt % NiO considerably reduces the temperature of
the (metastable) anatase to rutile phase transition,
temperature (td ~ 380°C) and their thermolysis gives
particles uniform in size. The purity of samples was
checked using the PGS 2 and an SRM 25 Xꢀray anaꢀ
lyzer. The net impurity content was within 0.05 wt %.
which was reported to begin at 600°
pletion at 900° [1, 3, 12]. There is, however, still no
general agreement as to the effect of NiO additions on
С and reach comꢀ
С
The average crystallite size was evaluated from the
the anatase to rutile phase transition. In addition, it is width of Xꢀray diffraction peaks and by electron
488

PHASE TRANSFORMATIONS IN THE TiO2–NiO SYSTEM
Table 1. Preparation conditions and composition of starting mixtures
489
History
Weight percent
Mixture
TiO2
Anatase from HTD Ni(NO3)2
NiO
TiO2
NiO
I
II
⋅
6H2O calcined at 800°C
95.0
95.0
95.0
95.0
95.0
48.3
48.3
48.3
48.3
97.0
90.0
85.0
48.3
5.0
5.0
Anatase from HTD (NiOH)2CO3 calcined at 800°C
Anatase from HTD Ni(NO3)2 6H2O
Anatase from HTD (NiOH)2CO3
Anatase from TTB Ni(NO3)2 6H2O
Anatase from HTD (NiOH)2CO3
III
IV
⋅
5.0
5.0
V
⋅
5.0
VI
51.7
51.7
51.7
51.7
3.0
VII
VIII
IX
X
Anatase from TiCl4 Ni(NO3)2
Anatase from HTD Ni(NO3)2
⋅
⋅
6H2O
6H2O
Anatase from TiCl4 (NiOH)2CO3
Anatase from HTD (NiOH)2CO3
Anatase from HTD (NiOH)2CO3
Anatase from HTD (NiOH)2CO3
XI
XII
XIII
10.0
15.0
51.7
HTD
Ni(NO3)2 ⋅ 6H2O
in this temperature range was 1.0%. No events were
detected at temperatures from 200 to 600 , and the
weight loss in this temperature range was 0.7%. Active
desulfating began at 700–710 and reached the highꢀ
est rate at 780 . At 780 , we observed the most
rapid release of sulfur oxides ( = 64 and = 48).
The small exothermic peak at ~ 850 , with no
weight change, is attributable to the anatase to rutile
polymorphic transformation ( = 1.8 kJ/mol).
microscopy and was found to be
d
20 nm for NiO,
ꢀ
°
C
d
20 nm for anatase, and 60 nm for rutile.
d
ꢀ
ꢀ
TiO2 + NiO mechanical mixtures (Table 1) were
°
С
prepared by thoroughly mixing titanium(IV) oxides,
nickel(II) salts, and their calcination products in an
agate mortar until the powder was uniform in color.
°
С
°С
m
/
e
t
m/e
°
C
Mixtures I–XIII were calcined in air in porcelain
crucibles at temperatures from 600 to 1200°
the calcination, the temperature was maintained conꢀ
stant to within . The homogeneity of the resultꢀ
С. During
Δ
H
Thermal analysis of the anatase prepared through
3 C
°
TiCl4 thermolysis (Fig. 1b) showed no desorption
ant materials was checked by determining NiO conꢀ
tent on an ARL 3410 ICP optical emission spectromꢀ
eter (at NiO contents under 15 wt %) and by
potentiometric titration of equimolar mixtures.
endotherms. The exothermic peak around 852 C
°
seems to arise from the anatase to rutile phase transiꢀ
tion. No chlorine release was detected during the
phase transition.
In the case of the TiO2 prepared from TTB
(Fig. 1c), we observed endothermic peaks at temperaꢀ
Electronꢀmicroscopic examination showed that
the calcination of the TiO2 + NiO mixtures yielded
agglomerates on the order of 1 m in size.
µ
tures from 50 to 180
°
C
, due to water desorption. Heatꢀ
The phase composition of the samples was deterꢀ
mined by Xꢀray diffraction on a DRONꢀ3M powder
ing to 180–400
°
C predominantly removed volatile
thermolysis products, with a 15% weight loss. In this
temperature range, the most rapid release of organics
diffractometer (Co
K or CuK radiation). Thermoꢀ
α
α
gravimetric (TG) analyses were carried out in a
Netzsch Jupiter thermoanalytical system. The samꢀ
was observed at 245
°
C. The peaks at temperatures
from 450 to 620 are attributable to the oxidation of
°
C
ples were heated to 1200
°
C
at 20 C/min in an oxyꢀ
°
the thermolysis products.
gen–argon mixture. Electronꢀmicroscopic characterꢀ
ization was performed on a JEOL 6450.
The temperature of the anatase–rutile phase tranꢀ
sition depends on the history of the titanium dioxide
(Fig. 2). The phase transition of the TiO2 prepared
RESULTS AND DISCUSSION
from HTD begins at 850
°C and reaches completion at
900 (3 h) or 950 (1 h), whereas that of the TiO2 preꢀ
°
C
Anatase–rutile phase transition in the TiO2–NiO
system. The differential thermal analysis (DTA) curve
of the anatase prepared from HTD showed a small
pared from TiCl4 reaches completion at a 100°C
higher temperature.
endotherm at temperatures from 32 to 200
°
С, which
To examine the influence of nickel oxide additions
was due to water removal (Fig. 1a). The weight change with different histories on the phase composition of
INORGANIC MATERIALS Vol. 48
No. 5 2012

490
VIKTOROV et al.
I
×
1011, А
(a)
DSC, mV
EXO
ТG, %
102
DTG, %/min
0.8
CO2, m/e = 44
2
7
101
100
99
0.6
6
0
0.4
5
1.00%
–2
–4
0.2
4
0.70%
698.2
ТG
°
C
–3.44%
–0.12%
0
3
98
161%
DTG
779.0
–0.2
2
97
°
C
–6
–8
DTA
–0.4
1
96
SO2, m/e = 64
SO, m/e = 48
–0.6
0
200
400
600
Temperature,
800
C
1000
°
DSC, mV
EXO
(b)
ТG, %
115
4
110
105
100
2
852.1°C
DTA
0
DTG
ТG
= 36
–2
Cl,
m
/e
95
90
–4
0
100
200
300
400
500
600
700
800
900
Temperature,
°
C
Fig. 1. Thermal analysis/mass spectrometry of pure anatase prepared from (a) HTD, (b) TiCl , and (c) TTB.
4
fineꢀparticle TiO2–NiO oxides, we prepared mixtures decomposition of the nickel nitrate and basic nickel
I–IV. carbonate. After calcination of pure anatase and mixꢀ
tures I–IV at temperatures from 600 to 750
phase transition was detected.
°
C, no
The thermal analysis results for mixtures I–IV were
essentially identical to those for pure anatase. The
observed changes in the endothermic peaks in the
It is worth pointing out that nickel oxide additions
temperature range 200–400°C were due to the had a significant effect on the rate and temperature
INORGANIC MATERIALS Vol. 48
No. 5
2012

PHASE TRANSFORMATIONS IN THE TiO2–NiO SYSTEM
491
109, А
(c)
DSC, mV
EXO
I
×
TG, %
100
900
800
700
600
500
400
300
200
100
0
–5.77%
3.0
2.5
TG
95
90
85
80
75
70
DSC
–11.82%
2.0
1.5
1.0
0.5
0
–30.75%
–3.41%
H2O
–2.55%
–1.81%
–5.43%
CO2
400
200
600
800
1000
t, °C
Fig. 1. (Contd).
α
(а)
1.2
1.0
0.8
0.6
0.4
0.2
120
100
80
60
40
20
0
5
4
3
4
3
1
2
2
1
0
α
10
20
30
(b)
40
50
60
70
Time, min
1.2
5
750
850
950
1050
Temperature, °C
1150
1.0
0.8
0.6
0.4
0.2
4
3
2
Fig. 2. Percent of rutile obtained from anatase as a funcꢀ
tion of calcination temperature: anatase prepared by heatꢀ
treating (
1
1, 3) TiCl and (2, 4) HTD for (1, 2) 1 and
4
(3, 4) 3 h.
0
10
20
30
(c)
40
50
60
70
Time, min
α
1.2
1.0
0.8
0.6
0.4
0.2
range of the anatase to rutile phase transition. Moreꢀ
over, the oxides prepared from basic nickel carbonate
and nickel nitrate had different effects (Fig. 3). In the
case of the NiO prepared from nickel nitrate, the rate
of the anatase–rutile phase transition was considerꢀ
ably higher in comparison with the carbonate NiO.
2, 3, 4, 5
1
According to Xꢀray diffraction data, the rate of the
anatase–rutile phase transition increases with nickel
oxide content, but the rutile yield remains constant or
even decreases starting at 10 wt % NiO (Fig. 4).
Nickel titanate formation in equimolar fineꢀparticle
anatase + NiO oxide mixtures. Equimolar (in terms of
0
10
20
30
40
50
60
70
Time, min
Fig. 3. Anatase to rutile conversion as a function of calciꢀ
nation time at (a) 800, (b) 850, and (c) 900 : ( ) anatase,
) mixture I, ( ) mixture II, ( ) mixture IV, (5) mixture III.
°C 1
(2
3
4
INORGANIC MATERIALS Vol. 48
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492
VIKTOROV et al.
93
92
91
90
89
88
87
86
85
84
120
100
80
60
40
20
0
2
4
3
1
83
700
750
800
850
10
20
30
40
50
60
Temperature, °C
wt % NiO
Fig. 4. Rutile yield as a function of nickel oxide content for
Fig. 5. Nickel titanate content as a function of calcination
temperature for mixtures ( ) VII, ( ) VIII, ( ) IX, and
) X calcined for 3 h.
the polymorphic transformation during calcination at
1
2
3
800°
C
for 1 h.
(4
NiO) TiO2 + (NiOH)2CO3 and TiO2 + Ni(NO3)2
⋅
to Xꢀray diffraction data, the sample calcined at 600°C
6H2O mixtures differ in the conditions of nickel titanꢀ consisted of an equimolar TiO2 + NiO mixture, with
ate formation, as evidenced by the phase composition no nickel titanate. Active NiTiO3 formation begins just
of calcined samples (Table 2). Nickel nitrate ensures a above 600°C. At a calcination temperature of 700°C,
higher nickel titanate yield (Fig. 5).
the NiTiO3 yield was 81 wt %, and no anatase–rutile
phase transition occurred. The transition was observed
above 700°C and reached completion at 800°C. The
NiTiO3 yield at this temperature was 92 wt %. Further
raising the calcination temperature produced insignifꢀ
icant changes.
The titanium dioxide prepared via the chloride
route was the most effective for nickel titanate formaꢀ
tion. The anatase–rutile phase transition then began
at a 50°C higher temperature in comparison with the
anatase prepared via the sulfate route. Nickel titanate
formation reaches completion after a complete anaꢀ
tase to rutile phase transition in the temperature range
CONCLUSIONS
700–850°C.
The effect of NiO content on the anatase to rutile
phase transition in fineꢀparticle TiO2–NiО oxides has
been studied using Xꢀray diffraction, differential therꢀ
mal analysis, and electron microscopy.
The use of HTD (mixture XIII) instead of titanium
dioxide activates nickel titanate formation. According
Nickel oxide promotes rutile formation and
reduces the temperature of the anatase to rutile phase
transition. In addition, the polymorphic transformaꢀ
tion temperature depends on the history of both
nickel(II) oxide and titanium(IV) oxide.
Table 2. Phase composition of the calcined mixtures
Weight percent
Mixture
t, °C
anatase rutile
NiO
NiTiO3
In the temperature range 700–850°C, nickel titanꢀ
Calcination for 3 h
ate, NiTiO3, forms only from anatase, after a complete
anatase to rutile phase transition. In the case of the
NiO prepared from nickel nitrate, the rate of the anaꢀ
tase–rutile phase transition is considerably higher in
comparison with nickel carbonate and nickel oxalate.
Rutile does not react with NiO in this temperature
range.
Anatase prepared through HTD thermolysis
ensures the most effective solidꢀstate synthesis of
nickel titanate.
I
700
800
850
700
800
850
95
0
0
95
95
0
5
5
5
5
5
5
0
tr
tr
0
0
II
95
12
0
83
100
0
0
Calcination for 1 h
III
IV
700
800
850
700
800
850
35
tr
0
33
28
0
33
30
26
48
45
44
32
37
46
tr
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