X-ray and thermochemical investigations on SrUTeO6 and SrUTe2 O8

Article abstract of DOI:10.1016/S0925-8388(01)01934-X

Two quaternary compounds SrUTeO₆ and SrUTe₂O₈ were identified and characterized in the Sr-U-Te-O system. The lattice cell parameters for both compounds were refined and indexed on the monoclinic system. The thermal charact

Full text of DOI:10.1016/S0925-8388(01)01934-X

Journal of Alloys and Compounds 337 (2002) 248–253
L
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X-ray and thermochemical investigations on SrUTeO and SrUTe O
6
2
8
*
K. Krishnan, S.K. Sali, G.A. Rama Rao, Smruti Dash, K.D. Singh Mudher , V. Venugopal
Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
Received 7 June 2001; accepted 29 October 2001
Abstract
Solid state reactions of SrUO and TeO in 1:1 and 1:2 molar ratio led to the formation of two new quaternary compounds SrUTeO
6
4
2
and SrUTe O . The compounds were characterised by X-ray and thermal methods. X-ray powder diffraction data of both the compounds
2
8
were indexed on the monoclinic system. The standard Gibbs free energy of formation (D G8, T) data of SrUTeO (s) and SrUTe O (s)
f
6
2
8
were obtained by the vapour pressure measurement of TeO (g) over these systems by employing the Knudsen effusion mass loss (KEML)
2
technique and could be represented by the relation:
2
1
D G8SrUTeO (s) 5 (22180.7 1 0.4263T (K))630 kJ mol [1080–1162 K]
f
6
2
1
D G8SrUTe O (s) 5 (22502.6 1 0.5816T (K))630 kJ mol [955–1041 K]
f
2
8

2002 Elsevier Science B .V . All rights reserved.
Keywords: Actinide compounds; Thermodynamic properties; X-ray diffraction; Thermal analysis
1
. Introduction
2. Experimental
Tellurium is one of the highly corrosive fission products
2.1. Preparation and characterisation of the compounds
SrUTeO (s) and SrUTe O (s) were prepared by heating
that can interact with fissile elements and other fission
products of the oxide fuels within the reactor forming
binary and ternary oxides [1]. Barium and strontium are
the alkaline earth fission products which form insoluble
oxide phases in the fuel matrix. Tellurium can also react
with these fission products forming ternary and quaternary
compounds. A number of uranates of strontium and
tellurium are reported in the literature [2–6]. In the
quarternary system, preparation of the double tellurates of
actinides and alkaline earth metals with uranium(VI)
corresponding to the general formula M UO (TeO ) and
6
2
8
a mixture of SrUO (s) and TeO (s) in a 1:1 and 1:2 molar
4
2
ratio in argon atmosphere at 1075 K. Strontium uranate
SrUO (s), was prepared by heating a mixture of SrCO (s)
4
3
and U O (s) in a 3:1 molar ratio in a furnace in air
3
8
atmosphere at 1225 K. The products were removed
intermittently, ground and reheated to obtain pure phases
of the compounds. The formation of the compound was
confirmed from their X-ray diffraction patterns recorded on
a Diano X-ray diffractometer using graphite monochromat-
3
2
3 4
M U(TeO ) , where M5Ba or Ca have been reported in
ized Cu Ka radiation (l50.15406 nm).
2
3
5
1
the literature [7]. However, there are no such data available
in the literature on Sr–U–Te–O quaternary systems. In
continuation of our earlier studies on the ternary systems
of tellurium-bearing compounds [8–10], we report the
X-ray, thermal and Gibbs free energy of formation of the
two new phases SrUTeO (s) and SrUTe O (s) in this
2.2. TG and DTA measurements
The thermal behaviour of SrUTeO (s) and SrUTe O (s)
6 2 8
was studied by recording their TG and DTA patterns
simultaneously in the ULVAC thermal analyser. The
experiments were carried out in air in alumina cups at a
heating rate of 10 K/min up to 1473 K. Preheated sintered
alumina was used as the reference material in DTA
experiments.
6
2
8
paper.
*
Corresponding author. Fax: 191-22-550-5151.
E-mail address: kdsingh@apsara.barc.ernet.in (K.D. Singh Mudher).
0
925-8388/02/$ – see front matter
 2002 Elsevier Science B .V . All rights reserved.
PII: S0925-8388(01)01934-X

K. Krishnan et al. / Journal of Alloys and Compounds 337 (2002) 248–253
249
Table 2
2
.3. Vapour pressure measurements
X-ray diffraction data of SrUTe O ; a51.3038(3) nm, b50.5434(3) nm,
2
8
c51.2516(3) nm, b593.318(3) , (l50.15406 nm)
The mass loss measurements were carried out in a Cahn
vacuum microbalance by the Knudsen effusion mass loss
KEML) technique. Boron nitride cell with an orifice
diameter of ¯1.0 mm at the center of the lid was used as
the Knudsen cell. Detailed experimental set-up and the
Clausing factor calibration for the Knudsen cell have been
described in our earlier studies [11].
h k l
2 0 0
dobs (nm)
dcal (nm)
I/I0
(
0.6487
0.5746
0.4639
0.3423
0.3303
0.3253
0.2882
0.2818
0.2708
0.2627
0.2346
0.6508
0.5763
0.4642
0.3420
0.3306
0.3254
0.2882
0.2820
0.2708
0.2625
0.2348
0.2345
0.2252
0.2169
0.2018
0.2018
0.1973
0.1945
0.1945
0.1925
0.1870
0.1747
0.1718
0.1695
0.1694
0.1655
0.1653
0.1653
34
18
26
28
96
100
43
51
20
12
09
2
2
1 0 2
2 0 2
2
0
4
0 3
1 3
0 0
2
2 0 4
4
0
0 2
1 4
3
. Results and discussion
1 1 4
1 0
2 2 2
2 1
2 2 3
5
2
2
3
.1. Characterisation by XRD
3
0.2251
0.2169
0.2018
10
09
70
The X-ray diffraction patterns of SrUTeO (s) and
6
22 0 6
SrUTe O (s) formed by reacting SrUO (s) and TeO (s) in
6 0 0
2
8
4
2
6
5
0
1 1
0 4
1 6
0.1972
0.1943
18
12
the ratio of 1:1 and 1:2 in argon at 1023 K, were different
from those of the reported phases in Sr–U–O, Sr–Te–O
and U–Te–O systems [12]. Alternatively, these com-
pounds were also obtained by heating mixtures of SrO(s)
and UTeO (s) and SrTeO (s) and UTeO (s) in the respec-
2
2
5 1 4
5 2 1
0.1924
0.1869
0.1747
0.1717
0.1695
12
09
09
36
35
22 0 7
2
5
3
5
7 1 2
2 0
tive molar ratios under similar conditions. The X-ray
powder diffraction data of SrUTeO (s) and SrUTe O (s)
6
6
2
8
2
2
2
1 1 7
6 2 2
7 1 3
0 2 6
were indexed on the monoclinic system. The refined cell
parameters and the indexed diffraction data of both the
compounds are given in Tables 1 and 2, respectively.
0.1655
09
3
.2. Thermal behaviour in air
showed condensation of TeO (s) at the cooler part of the
2
reaction tube, confirming the volatilization of TeO (s). The
2
The decomposition of SrUTe O (s) takes place in a
thermal decomposition of SrUTe O (s) in air could be
2
8
2
8
single step in the temperature range of 975–1400 K
represented by Eq. (1)
forming SrUO (s), as identified from its XRD pattern.
4
XRD analysis of the volatile product of SrUTe O (s)
SrUTe O (s) → SrUO (s) 1 2TeO (g)
(1)
2
8
2
8
4
2
Table 1
X-ray diffraction data of SrUTeO ; a51.3579(3) nm, b50.9766(2) nm, c50.9903(2) nm, b5107.168(2), (l50.15406 nm)
6
h k l
dobs (nm)
dcal (nm)
I/I0
h k l
4 0 1
21 2 3
21 0 4
21 1 4
0 4 2
dobs (nm)
dcal (nm)
I/I0
1
2
2
0
0 1
0.6758
0.6482
0.4737
0.4338
0.3539
0.3470
0.3399
0.6752
0.6486
0.4736
0.4339
0.3541
0.3472
0.3400
0.3397
0.3313
33
17
23
16
28
48
40
0.2823
0.2731
0.2457
0.2387
0.2168
0.2055
0.2018
0.2822
0.2732
0.2458
0.2384
0.2169
0.2054
0.2016
22
20
13
16
09
24
26
0 0
0 1
2 1
2
2
3 1 2
1 2 2
23 4 2
1 2 4
2
0
2 1
2 2
2
2 2 2
0.3313
0.3255
0.3190
40
0 4 3
0.1931
0.1879
0.1806
0.1931
0.1931
0.1878
19
16
14
1
5 0
0
4
2
3 0
0 0
1 2
0.3255
0.3243
0.3191
100
40
5 2 2
2 5 1
0.1806
0.1805
0.1749
0.1712
0.1629
0.1628
0
5 2
2
2
4 0 2
1 3 1
0.3141
0.3060
0.3000
0.3143
0.3062
0.3000
0.2999
0.2909
25
26
44
6 1 2
3 5 1
27 2 4
0 6 0
0.1750
0.1713
0.1628
14
26
14
0
1 3
3 2 2
3 0
2
2
0.2908
40

2
50
K. Krishnan et al. / Journal of Alloys and Compounds 337 (2002) 248–253
The plot of alpha (a), the fractional weight loss (a 5
w 2 w )/(w 2 w ), where w , w and w are the mass at
initial, final and at temperature T) versus temperature for
iometric compounds in Sr–U–O system in sealed vacuum
ampoules and have reported the structural analysis of the
stable phase SrUO3.597(s). The XRD data of SrUO3.597(s)
obtained in our studies (Eq. (2)), could be indexed on the
hexagonal system with cell parameters a53.996(4) and
(
i
T
i
f
i
f
T
the compound SrUTe O (s) and pure TeO (s) is shown in
2
8
2
Fig. 1. The a plots of SrUTe O (s) and TeO (s) are similar
2
8
2
˚
indicating that the kinetics of decomposition of the com-
c518.506(6) A. These values are in close agreement with
pound is controlled by the evaporation of TeO (g).
the values reported by Takahashi et al. [13] and Fujino et
al. [14]. The thermal stability of various nonstoichiometric
alkaline earth monouranates in different atmospheres up to
1273 K, have been reported by Tagawa et al. [15]. They
have identified the formation of various nonstoichiometric
strontium uranates such as SrUO3.563(s), SrUO3.997(s),
SrUO3.673(s) and SrUO3.175(s) in different atmospheres on
2
The DTA curve of SrUTe O (s) showed an endothermic
2
8
peak at 1213 K due to the melting of the compound before
decomposition, as shown in Fig. 1. In the case of
SrUTeO (s), the decomposition is accompanied by melting
6
of the compound at 1208 K. The DTA showed a broad
endothermic peak due to its decomposition occurring over
a wide range of temperatures. The final product of
heating SrUO (s) in vacuum, air, carbon dioxide, and
4
decomposition of SrUTeO (s) in air was also identified as
hydrogen, respectively.
6
SrUO (s).
The equilibrium vapour pressures of TeO (g) and
4
2
0
.2015 O (g) were derived in the temperature range of
2
3
3
.3. Vapour pressure measurements
1080–1162 K over a mixture of SrUTeO (s) and
6
SrUO3.597(s). The total mass loss due to TeO (g) and
2
.3.1. SrUTeO6
O (g) was apportioned in terms of their molar masses and
2
The vapour pressure measurements by KEML technique
could be given as:
were first carried out for SrUTeO (s), in order to obtain
6
dw/dt 5 (dw /dt) 1 (dw /dt)
(3)
1
2
D G8 (SrUTeO , s, T), since this value has been used to
f
6
calculate the Gibbs free energy formation of SrUTe O (s)
in the subsequent experiments.
Under the conditions of measurements of partial pres-
sure of the evolved gases, the thermal decomposition of
2
8
where dw/dt is the experimentally measured combined
rate of mass loss of TeO (g) and O (g), dw /dt and
2
2
1
dw /dt are the individual rate of mass losses of TeO (g)
2
2
and O (g), respectively. A similar apportionation pro-
2
SrUTeO in vacuum is represented by Eq. (2)
6
cedure has been followed in our earlier studies on Ni TeO
3
6
compound in the Ni–Te–O system and Cr TeO (s) and
SrUTeO (s) → SrUO
(s) 1 TeO (g) 1
2
6
6
3.597
2
Fe TeO (s) in the Cr/Fe–Te–O systems [9,16]. The
2
6
0
.2015 O (g) [1080–1162 K]
(2)
2
mathematical derivation for the rate of mass loss is, using
Eq. (3),
The formation of nonstoichiometric SrUO3.597(s), a dark
green product, in vacuum was identified from its XRD
pattern. Takahashi et al. [13] have prepared nonstoich-
dw /dt 5 [(dw/dt).(792.10/824.1)]
1
5
(dw/dt).(0.9612)
(4)
By substituting the value of dw /dt in Eq. (3), dw /dt
1
2
can be calculated. Thus by inserting the individual mass
loss of dw /dt and dw /dt in the rate of mass loss Eq. (5)
1
2
2
3
p (Pa) 5 [(dw/dt).(1/kA).(2.28 3 10 ).œT/M]
(5)
where p is the partial pressures of the evolved gas, k is the
Clausing factor, A is the area of the orifice diameter, T is
the temperature and M is the molecular weight of the
evolved gaseous species, the individual partial pressures
contributed by TeO (g) and O (g) were determined and
2
2
are given in Table 3. The corresponding least squares fit of
log p of TeO (g) with 1/T is shown in Fig. 2 and could be
2
represented by the relation:
log p
(kPa)60.03 5 2 8119.9/T (K)
TeO (g)
2
1
5.0535 [1080–1162 K]
(6)
The least squares fit of log p of O (g) versus 1/T can be
Fig. 1. The plot of a versus temperature for (A) SrUTe O , (B) TeO
2
2
2
8
and (C) DTA of SrUTe O in air.
given as:
2
8

K. Krishnan et al. / Journal of Alloys and Compounds 337 (2002) 248–253
251
Table 3
Gibbs free energy of formation of SrUTeO (s) at different temperatures
6
Temperature
K)
pTeO2(g)
(kPa)310
p8TeO2(g)
(kPa)310
pO2(g)
(kPa)310
D G8SrUTeO (s)
(kJ mol )
f
6
2
3
23
24
21
(
1
1
1
1
1
1
1
1
1
080
092
099
114
121
129
140
150
162
3.60
4.30
4.70
5.60
6.01
6.62
8.70
9.50
11.0
86.1
111.9
130.1
178.4
206.1
242.6
302.4
368.1
463.9
1.5
1.8
1.9
2.3
2.4
2.7
3.2
3.6
4.0
21720.3
21715.2
21712.2
21705.8
21702.8
21699.4
21694.7
21690.5
21685.3
2
1
log p
(kPa)60.01 5 2 6872/T
estimation is within 620 kJ mol
[19]. To evaluate,
O (g)
2
D G8 (T) values for unknown compounds in the Sr–U–O
f
m
1
2.5343 [1080–1162 K]
(7)
system, maximum possible chemical reactions should be
written, in terms of the ternary oxides. The chemical
reactions considered are:
The standard Gibbs free energy of formation of
SrUTeO (s) is represented by the relation:
6
SrUO (s) 1 0.052 U O (s) 5 SrUO
(s) 1 0.156 UO (s)
3
4
3
8
3.948
D G8SrUTeO (s) 5 D G8SrUO
(s) 1 D G8TeO (l)
f 2
f
6
f
3.597
(
9)
1
0.2015 RT ln p
O (g)
2
SrUO3.948(s) 1 0.171 U O (s) 5 SrUO3.777(s)
1
RT ln ( pTeO2 /p8TeO2
)
(8)
3
8
1
0.513 UO (s)
(10)
(11)
3
where pTeO2 is the measured vapour pressure data (Eq.
6)), p8TeO is the partial pressure of TeO (g) over
(
2
SrUO3.777(s) 1 0.0546 U O (s) 1 0.0418 U O (s)
3 8 4 9
2
TeO (l) and the vapour pressure data are taken from the
2
5
SrUO3.597(s) 1 0.331 UO (s)
3
literature [17,18].
The experimental D G8(SrUO
reported in the literature. So the estimation of
s, T) values are not
3.597,
f
SrO(s) 1 0.2776 U O (s) 1 0.0418 U O (s) 5 SrUO3.597(s)
3
8
4
9
D G8(SrUO3.597, s, T) was carried out using the method
(12)
f
suggested by Lindemer et al. [19]. In this method, either
D H8 (298.15 K) or D G8 (T) value of at least one of the
SrO(s) 1 0.052 U O (s) 1 0.844 UO (s) 5 SrUO3.948(s)
3 8 3
f
m
f
m
ternary compounds in the required system should be
experimentally known. Error involved in this type of
(
(
13)
14)
SrO(s) 1 0.223 U O (s) 1 0.331 UO (s) 5 SrUO3.777(s)
3
8
3
SrUO3.948(s) 1 SrUO3.597(s) 1 0.0072 U O (s)
3
8
5
2 SrUO3.777(s) 1 0.0054 U O (s)
(15)
(16)
4
9
For any chemical reaction, one can write:
D G8 (T) 1 c 5 0
r
m
where c is a constant and can be positive (reaction
favorable), negative (reaction not favorable) or zero
(equilibrium). For each of these chemical Eqs. (9)–(15),
one can yield an expression of the type given by Eq. (16).
By substituting known D G8 (T) values for SrUO (s),
f
m
4
U O (s), U O (s) and UO (s) from the literature [20,21]
3
8
4
9
3
and T 5 900 K in each expression the following equations
are obtained:
Fig. 2. Temperature dependence of the vapour pressure of TeO (g) over
2
(
A) SrUTeO (s) and SrUO
(s), and (B) SrUTe O (s) and SrUTeO (s).
G(SrUO3.948) 1 1659775 1 a 5 0
(17)
6
3.597
2
8
6

2
52
K. Krishnan et al. / Journal of Alloys and Compounds 337 (2002) 248–253
G(SrUO3.777) 2 G(SrUO3.948) 2 675 1 b 5 0
G(SrUO3.597) 2 G(SrUO3.777) 2 6252 1 c 5 0
G(SrUO3.597) 1 1490558 1 d 5 0
(18)
(19)
(20)
(21)
(22)
3.3.2. SrUTe O
2
8
SrUTe O (s) on heating in vacuum, during the vapour
2
8
pressure measurements by the KEML technique, decom-
poses with the formation of SrUTeO (s) as an intermediate
6
product. The XRD pattern of the product obtained from the
reaction was similar to that of the compound formed by
heating a mixture of SrO and UTeO5 in 1:1 molar
proportion as discussed in Section 3.1. Hence, the de-
composition of SrUTe O (s) could be represented as:
G(SrUO3.948) 1 1497485 1 e 5 0
2
8
G(SrUO3.777) 1 1496809 1 f 5 0
SrUTe O (s) → SrUTeO (s) 1 TeO (g) [955–1041 K]
2
8
6
2
2
G(SrUO3.777) 2 G(SrUO3.948) 2 G(SrUO3.597) 1 751 1 g
(27)
5
0
(23)
Further decomposition of SrUTeO (s) in similar ex-
6
where G(SrUO3.948), G(SrUO3.777) and G(SrUO3.597) rep-
resent the D G8 (900 K) for SrUO3.948(s), SrUO3.777(s)
perimental conditions takes place as given in Eq. (2).
The equilibrium vapour pressure of TeO (g) over a
f
m
2
and SrUO3.597(s), respectively. By eliminating the un-
known Gibbs energy of formation values algebraically
from the above equalities one gets:
mixture of SrUTe O (s) and SrUTeO (s) was calculated in
the temperature range of 955–1041 K for the reaction
shown in Eq. (27) and the values are given in Table 4. The
2
8
6
corresponding least squares fit of log p of TeO (g) versus
2
a 1 b 1 2c 2 d 1 e 2 f 1 g 5 2 157472
(24)
1
/T for SrUTe O is also shown in Fig. 2, and is
2 8
represented by Eq. (28):
This relationship is very useful because, it puts a
constraint on the permissible values of a, b, c, d, e, f and
g. The number of unknowns exceeds the number of
equations. Iteration method with an initial gauss value is
used to solve the above equation sets. The resulting
log p (kPa)60.01 5 2 12446.4/T (K)
1
8.9211 [955–1041 K]
(28)
By using the vapour pressure data of TeO (g), the
standard Gibbs free energy formation data of SrUTe O (s)
could be obtained from the relation:
2
D G8(T) values for the SrUO3.948(s), SrUO3.777(s) and
f
2
8
SrUO3.597(s) compounds are 21659, 21634.0 and
2
1
2
1606.5 kJ mol respectively, while the values of a, b, c,
d, e, f and g are 20.8, 224.32, 221.2, 116, 161.6, 137.2,
.7 kJ, respectively. This method of estimation has been
repeated for T 5 1000 K and 1100 K. D G8(SrUO3.597, s,
D G8SrUTe O (s) 5 D G8SrUTeO (s) 1 D G8TeO (l)
f
2
8
f
6
f
2
1
1
RT ln [pTeO /p8TeO2]
(29)
f
2
2
1
T) value is calculated as 21572.0 kJ mol at 1000 K and
2
1
2
1537.9 kJ mol at 1100 K. Least squares analysis of
Using the vapour pressure data of pTeO2 from the
D G8(SrUO3.597, s, T) values as a function of temperature
can be given as:
experimental study of Eq. (28), the values of p8TeO2 and
D G8TeO (l) from the literature [17,18] and the Gibbs free
f
f
2
energy of formation of SrUTeO (s) from Eq. (26), the
6
D G8(SrUO3.597, s, T) 5 2 1915.1 1 0.343 T
(25)
f
Gibbs free energy formation of SrUTe O (s) was calcu-
2
8
lated and the values are given in Table 4, and is repre-
sented by Eq. (30)
The first term of the above equation corresponds to
enthalpy of formation at average temperature (1000 K).
2
1
D H8 (SrUO3.597, s, 1000 K) value (21915.1 kJ mol
)
Table 4
f
m
Gibbs free energy of formation of SrUTe O (s) at different temperatures
calculated in the present work is in good agreement with
2
8
2
1
D H8 (SrUO3.522, s, 298.15 K) value (21893.1 kJ mol
)
Temperature
(K)
pTeO
(kPa)310
p8TeO
(kPa)310
D G8SrUTe O (s)
(kJ mol )
f
m
(g)
2
(s)
f
2
8
2
2
4
23
21
determined by Takahashi et al. [15] using solution
calorimetry.
By using the estimated Gibbs free energy formation
9
964
9
9
9
55
0.772
1.010
1.392
1.937
2.599
3.004
3.996
5.040
7.790
9.030
3.788
5.080
6.413
21947.2
21941.9
21936.1
21929.7
21923.9
21921.0
21915.2
21910.0
21901.2
21897.2
74
85
95
values for SrUO3.597(s) from Eq. (25) and that of TeO (l)
2
8.617
from the literature, the standard Gibbs free energy forma-
11.209
12.759
16.468
20.632
29.777
35.211
tion of SrUTeO (s) could be obtained and is represented by
6
1000
the relation:
1
010
019
1
D G8SrUTeO (s)630 kJ/mol 5 2 2180.7
f
6
1034
041
1
1
0.4263 T (K) [1080–1162 K]
(26)

K. Krishnan et al. / Journal of Alloys and Compounds 337 (2002) 248–253
253
2
1
[
4] P.J. Galy, G. Meunier, Acta Crystallogr. B 27 (1971) 608.
D G8SrUTe O (s)630 kJ mol 5 2 2502.6
f
2
8
[5] M. Tromel, Anorganish Chem. Institute 1, Frankfurt, Germany,
Private communications, 1984.
1
0.5816 T (K) [955–1041 K]
(30)
[
[
6] M. Tromel et al., Z. Anorg. Allg. Chem. 378 (1970) 232.
7] J. Wroblewska, A. Erb, J. Dobrowolski, W. Freundilich, Ann. Chim.
France 4 (1979) 353.
4
. Conclusion
Two quaternary
[
8] K. Krishnan, G.A. Rama Rao, K.D. Singh Mudher, V. Venugopal, J.
Nucl. Mater. 254 (1998) 49.
compounds
SrUTeO (s)
6
and
[9] K. Krishnan, G.A. Rama Rao, K.D. Singh Mudher, V. Venugopal, J.
Alloys Comp. 288 (1999) 96.
10] K. Krishnan, G.A. Rama Rao, K.D. Singh Mudher, V. Venugopal, J.
SrUTe O (s) have been identified and characterised in the
2
8
[
[
[
Sr–U–Te–O system for the first time. The lattice cell
parameters for both compounds have been refined and
indexed on the monoclinic system.
The thermal behaviour of both compounds has been
studied using TG and DTA in air. It is observed that the
decomposition of both compounds started with the loss of
TeO (g). The final product in air was identified as
SrUO (s) by the XRD method. However, the final product
in vacuum was identified as SrUO3.597(s) for both com-
pounds.
Alloys Comp. 307 (2000) 114.
11] K. Krishnan, G.A. Rama Rao, K.D. Singh Mudher, V. Venugopal, J.
Nucl. Mater. 230 (1996) 61.
12] Powder Diffraction File, (Inorganic Phases–1988), International
Centre For Diffraction Data, 1601, Park Lane, Swarth More, PA
9081-2389, USA, 1988.
13] K. Takahashi, T. Fujino, L.R. Morss, J. Solid State Chem. 105
1993) 234.
[14] T. Fujino, N. Masaki, H. Tagawa, Z. Kristallogr. 145 (1977) 299.
[15] H. Tagawa, T. Fujino, T. Yamashita, Inorg. Nucl. Chem. 41 (1979)
1729.
1
[
2
(
4
[
16] K. Krishnan, G.A. Rama Rao, K.D. Singh Mudher, V. Venugopal, J.
Alloys Comp. 316 (2001) 264.
17] E.H.P. Cordfunke, R.J.M. Konings (Eds.), Thermochemical Data for
Reactor Materials and Fission Products, North Holland, Amsterdam,
By using the vapour pressure data of TeO (g) obtained
2
by the KEML technique, the standard Gibbs free energy
formation of SrUTeO (s) and SrUTe O (s) are being
reported for the first time.
[
6
2
8
1
990.
[
[
[
[
18] M.S. Samant, S.R. Bhardwaj, A.S. Kerkar, S.N. Tripathi, S.R.
Dharwadkar, J. Nucl. Mater. 211 (1994) 181.
19] T.B. Lindemer, T.M. Basemann, C.E. Johnson, J. Nucl. Mater. 100
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