Thermochemistry of lanthanum zirconate pyrochlore

A. V. Radha; Sergey V. Ushakov; Alexandra Navrotsky

doi:10.1557/jmr.2009.0401

Thermochemistry of lanthanum zirconate pyrochlore

A. V. Radha, Sergey V. Ushakov, Alexandra Navrotsky

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67 Scopus citations

Abstract

A thermodynamic study was carried out to resolve discrepancies in the enthalpy of formation and related parameters for lanthanum zirconate pyrochlore. The homogeneity field for single phase pyrochlore formation was determined to be ̃33-35 mol% La₂O₃ at 1500 °C. High-temperature oxide melt drop solution calorimetry was performed in sodium molybdate and lead borate solvents on three compositions ranging from La_1.98Zr _2.01O7 to La_2.07Zr_1.95O₇. The enthalpy of formation from oxides at 25 °C, ΔH⁰ _f,ox, for stoichiometric lanthanum zirconate pyrochlore is -107.3 ±5.1 kJ/mol, and the standard enthalpy of formation from elements, ΔH⁰_f,el, is -4102.2 ± 6.0 kJ/mol. La ₂Zr₂O₇ pyrochlore was found by differential thermal analysis to be stable up to its melting point. The melting point and the fusion enthalpy of La₂Zr₂O₇ pyrochlore were measured as 2295 ± 10 °C and ̃350 kJ/mol, respectively.

Original language	English (US)
Pages (from-to)	3350-3357
Number of pages	8
Journal	Journal of Materials Research
Volume	24
Issue number	11
DOIs	https://doi.org/10.1557/jmr.2009.0401
State	Published - Nov 2009
Externally published	Yes

ASJC Scopus subject areas

General Materials Science
Condensed Matter Physics
Mechanics of Materials
Mechanical Engineering

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title = "Thermochemistry of lanthanum zirconate pyrochlore",

abstract = "A thermodynamic study was carried out to resolve discrepancies in the enthalpy of formation and related parameters for lanthanum zirconate pyrochlore. The homogeneity field for single phase pyrochlore formation was determined to be{\~ }33-35 mol% La2O3 at 1500 °C. High-temperature oxide melt drop solution calorimetry was performed in sodium molybdate and lead borate solvents on three compositions ranging from La1.98Zr 2.01O7 to La2.07Zr1.95O7. The enthalpy of formation from oxides at 25 °C, ΔH0 f,ox, for stoichiometric lanthanum zirconate pyrochlore is -107.3 ±5.1 kJ/mol, and the standard enthalpy of formation from elements, ΔH0f,el, is -4102.2 ± 6.0 kJ/mol. La 2Zr2O7 pyrochlore was found by differential thermal analysis to be stable up to its melting point. The melting point and the fusion enthalpy of La2Zr2O7 pyrochlore were measured as 2295 ± 10 °C and{\~ }350 kJ/mol, respectively.",

author = "Radha, {A. V.} and Ushakov, {Sergey V.} and Alexandra Navrotsky",

year = "2009",

month = nov,

doi = "10.1557/jmr.2009.0401",

language = "English (US)",

volume = "24",

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journal = "Journal of Materials Research",

issn = "0884-2914",

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AU - Radha, A. V.

AU - Ushakov, Sergey V.

AU - Navrotsky, Alexandra

PY - 2009/11

Y1 - 2009/11

N2 - A thermodynamic study was carried out to resolve discrepancies in the enthalpy of formation and related parameters for lanthanum zirconate pyrochlore. The homogeneity field for single phase pyrochlore formation was determined to be ̃33-35 mol% La2O3 at 1500 °C. High-temperature oxide melt drop solution calorimetry was performed in sodium molybdate and lead borate solvents on three compositions ranging from La1.98Zr 2.01O7 to La2.07Zr1.95O7. The enthalpy of formation from oxides at 25 °C, ΔH0 f,ox, for stoichiometric lanthanum zirconate pyrochlore is -107.3 ±5.1 kJ/mol, and the standard enthalpy of formation from elements, ΔH0f,el, is -4102.2 ± 6.0 kJ/mol. La 2Zr2O7 pyrochlore was found by differential thermal analysis to be stable up to its melting point. The melting point and the fusion enthalpy of La2Zr2O7 pyrochlore were measured as 2295 ± 10 °C and ̃350 kJ/mol, respectively.

AB - A thermodynamic study was carried out to resolve discrepancies in the enthalpy of formation and related parameters for lanthanum zirconate pyrochlore. The homogeneity field for single phase pyrochlore formation was determined to be ̃33-35 mol% La2O3 at 1500 °C. High-temperature oxide melt drop solution calorimetry was performed in sodium molybdate and lead borate solvents on three compositions ranging from La1.98Zr 2.01O7 to La2.07Zr1.95O7. The enthalpy of formation from oxides at 25 °C, ΔH0 f,ox, for stoichiometric lanthanum zirconate pyrochlore is -107.3 ±5.1 kJ/mol, and the standard enthalpy of formation from elements, ΔH0f,el, is -4102.2 ± 6.0 kJ/mol. La 2Zr2O7 pyrochlore was found by differential thermal analysis to be stable up to its melting point. The melting point and the fusion enthalpy of La2Zr2O7 pyrochlore were measured as 2295 ± 10 °C and ̃350 kJ/mol, respectively.

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Thermochemistry of lanthanum zirconate pyrochlore

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