Enthalpies of Formation of La1−xAxMnO3±δ (A=Ca and Sr) Measured by High-Temperature Solution Calorimetry

2002 ◽  
Vol 163 (1) ◽  
pp. 186-193 ◽  
Author(s):  
Lisbeth Rørmark ◽  
Svein Stølen ◽  
Kjell Wiik ◽  
Tor Grande
Keyword(s):  
High Temperature ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
High Temperature Solution ◽  
Temperature Solution

Energetics of Nitridophosphates PON and “LiNaPON Glasses”

1998 ◽  
Vol 547 ◽  
Author(s):  
F. Tessier ◽  
A. Le Sauze ◽  
R. Marchand ◽  
A. Navrotsky
Keyword(s):  
High Temperature ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
High Temperature Solution ◽  
Thermodynamic Studies ◽  
Temperature Solution

AbstractStructural analogies have been demonstrated between the β-cristobalite, α-quartz and moganite phases of PON and its isoelectronic analog SiO2. Whereas the energetics of silica are well established, no data exist for the energetics of formation of nitridophosphates. High temperature solution calorimetry was used to determine the energetics of PON samples and a series of “LiNaPON oxynitride” glasses. Enthalpies of formation were measured as -371.71 ± 4.45 kJ/mol and -356.14 ± 3.98 for β-cristobalite and amorphous PON respectively and as -961.88 ± 3.86 kJ/mol for a 9 wt% nitrogen containing LiNaPON glass. These values constitute the first set of energetics data necessary to achieve further thermodynamic studies on nitridophosphates.

Energetics in the brownmillerite-perovskite pseudobinary Ca2Fe2O5-CaTiO3

1994 ◽  
Vol 9 (12) ◽  
pp. 3121-3124 ◽  
Author(s):  
T.R.S. Prasanna ◽  
A. Navrotsky
Keyword(s):  
High Temperature ◽  
Random Distribution ◽  
Configurational Entropy ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
High Temperature Solution ◽  
Pseudobinary System ◽  
Octahedral Sites ◽  
Intermediate Phases ◽  
Temperature Solution

The energetics of intermediate phases in the Ca2Fe2O5-CaTiO3 pseudobinary system was determined by high temperature solution calorimetry. The results suggest that both the intermediate compounds Ca3Fe2TiO8 and Ca4Fe2Ti2O11 are entropically stabilized because their enthalpies of formation are positive with respect to a mixture of Ca2Fe2O5 and CaTiO3. At high temperatures, the configurational entropy of the random distribution of Fe and Ti ions on the octahedral sites appears sufficient to stabilize the intermediate phases. The enthalpies of formation from the oxides at 1073 K of Ca2Fe2O5, Ca3Fe2TiO8, and Ca4Fe2Ti2O11 are −45.0 ± 3.8, −123.7 ± 8.0, and −192.7 ± 11.2 kJ/mol, respectively. Their enthalpies of formation from the elements at 298 K are −2139.8 ± 4.4, −3798.4 ± 8.6, and −5447.3 ± 12.2 kJ/mol, respectively.

Athermochemical Investigation of the La-Sr-Cu-O System

1989 ◽  
Vol 169 ◽  
Author(s):  
Joseph Bularzik ◽  
Alexandra Navrotsky ◽  
Bruce Scott ◽  
Joe Bringley ◽  
Steve Trail
Keyword(s):  
High Temperature ◽  
Alkaline Earth ◽  
High Temperature Superconductors ◽  
Solution Calorimetry ◽  
Alkaline Earth Metals ◽  
Heats Of Formation ◽  
High Temperature Solution ◽  
Calorimetric Measurements ◽  
Temperature Solution ◽  
The Stability

AbstractThe perovskite related La2‐xMxCuO4‐y oxides substituted with alkaline earth metals were one of the first classes of high temperature superconductors discovered. Determining the thermodynamic properties is important to understand the stability and superconducting mechanism of these structures. High temperature solution calorimetry, using a molten lead borate solvent, has been performed on La2CuO4 and the related Sr substituted oxides. Calorimetric measurements on CuO, La2O3 and SrCO3 yield heats of formation. A change in the trend of the heats of formation appears at Sr content 0.1, the reported orthorhombic to tetragonal transition, the onset of superconductivity and loss of oxygen.

High temperature solution calorimetry. Part 1. Development of a spherical solution calorimeter

1967 ◽  
Vol 45 (4) ◽  
pp. 383-388 ◽  
Author(s):  
R. Baboian ◽  
D. Laing ◽  
S. N. Flengas
Keyword(s):  
High Temperature ◽  
Solution Calorimetry ◽  
Temperature Sensing ◽  
High Temperature Solution ◽  
Reaction Cell ◽  
Spherical Shells ◽  
Inconel Alloy ◽  
Temperature Solution ◽  
Solution Calorimeter ◽  
Novel Design

A high temperature solution calorimeter of a novel design has been developed whereby the separated components are brought together and mixed within a completely enclosed, vacuum-sealed cell. The instrument consists of an inner spherical compartment containing the reaction cell, surrounded by a number of concentric spherical shells made of Inconel alloy. The calorimeter may be operated at temperatures up to 1 200 °C. The temperature-sensing circuit includes a differential thermopile, a d-c. microvolt amplifier, and a recording millivoltmeter. With this instrument calorific effects of the order of 0.1 cal could be detected.

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