Thermochemistry of rare earth perovskites Na3xRE0.67−xTiO3 (RE = La, Ce)

Dawei Feng; Pardha Saradhi Maram; Aleksandra Dorota Mielewczyk-Gryń; Alexandra Navrotsky

doi:10.2138/am-2016-5529

Thermochemistry of rare earth perovskites Na3xRE0.67−xTiO3 (RE = La, Ce)

Abstract

High-temperature oxide melt solution calorimetry using sodium molybdate (3Na2O·4MoO3) solvent at 973 K was performed for the Na3xRE0.67−xTiO3 (RE = La, Ce) perovskite series. The enthalpies of formation of lanthanum perovskites from oxides (La2O3, Na2O, TiO2), are −107.25 ± 2.56, −93.83 ± 6.06, −80.68 ± 5.93, and −33.49 ± 4.26 kJ/mol and enthalpies of formation from elements are −1614.05 ± 5.37, −1596.44 ± 7.68, −1594.03 ± 7.58, and −1577.56 ± 6.36 kJ/mol for Na0.459La0.522Ti0.999O3, Na0.454La0.523Ti0.994O3, Na0.380La0.567Ti0.980O3, and La0.692Ti0.979O3, respectively. The enthalpies of formation of cerium perovskites are −99.98 ± 5.78 and −45.78 ± 3.30 kJ/mol from oxides (Ce2O3, Na2O, TiO2), and −1611.34 ± 6.90 and −1602.06 ± 2.72 kJ/mol from elements for Na0.442Ce0.547Ti0.980O3 and Ce0.72Ti0.96O3. The A-site defect perovskites become more stable relative to oxide components as sodium contents increase. Na0.5Ce0.5TiO3 and Na0.5La0.5TiO3 could be considered as thermodynamically stable end-members in natural loparite minerals, in which these end-members are in solid solution with CaTiO3 and other components.

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Authors (4)

Dawei Feng dr
- University of California Davis Peter A Rock Thermochemistry Laboratory
Pardha Saradhi Maram Dr
- University of California Davis Peter A Rock Thermochemistry Laboratory
Aleksandra Dorota Mielewczyk-Gryń dr hab. inż.
Alexandra Navrotsky
- University of California Davis Peter A Rock Thermochemistry Laboratory

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Keywords

DROP SOLUTION CALORIMETRY

Details

Category:: Articles
Type:: artykuł w czasopiśmie wyróżnionym w JCR
Published in:: AMERICAN MINERALOGIST no. 101, pages 1125 - 1128,
ISSN: 0003-004X
Language:: English
Publication year:: 2016
Bibliographic description:: Feng D., Maram P., Mielewczyk-Gryń A., Navrotsky A.: Thermochemistry of rare earth perovskites Na3xRE0.67−xTiO3 (RE = La, Ce)// AMERICAN MINERALOGIST. -Vol. 101, nr. 5 (2016), s.1125-1128
DOI:: Digital Object Identifier (open in new tab) 10.2138/am-2016-5529
Verified by:: Gdańsk University of Technology