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Formation Enthalpies of Tetravalent Lanthanide Perovskites by High Temperature Oxide Melt Solution Calorimetry

Published online by Cambridge University Press:  01 February 2011

S. V. Ushakov
Affiliation:
Materials Science Department, California Institute of Technology, Pasadena, CA 91125, USA
J. Cheng
Affiliation:
Thermochemistry Facility, Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, CA 95616, USA
A. Navrotsky
Affiliation:
Thermochemistry Facility, Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, CA 95616, USA
J. R. Wu
Affiliation:
Materials Science Department, California Institute of Technology, Pasadena, CA 91125, USA
S. M. Haile
Affiliation:
Materials Science Department, California Institute of Technology, Pasadena, CA 91125, USA
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Abstract

High-temperature oxide melt solution calorimetry was used to measure formation enthalpies for several compositions of perovskites of nominal stoichiometry BaPrO3 and BaCeO3. Samples were synthesized from chemical solution methods followed by calcination at 1100-1300°C. PrO2 was synthesized by oxidation of Pr6O11 in an oxygen flow at 280°C. The samples were characterized by microprobe, thermogravimetric and differential thermal analyses. Cell parameters were refined by the Rietveld method. Barium excess in the samples with respect to ideal stoichiometry was detected. Drop solution enthalpies were measured in a Calvet type twin microcalorimeter, using 3Na2O·4MoO3 solvent at 702°C. Preliminary values of the formation enthalpy of BaPrO3 and BaCeO3 from oxides were -70 ±10 kJ/mol and -51 ±10 kJ/mol, respectively. They fall on the normal trend of energetics versus Goldschmidt tolerance factor and do not show any special stabilization of BaPrO3 relative to other MLnO3 perovskites.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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