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

Dawei Feng, Pardha Saradhi Maram, Aleksandra Mielewczyk-Gryń, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)1125-1128
Number of pages4
JournalAmerican Mineralogist
Volume101
Issue number5
DOIs
StatePublished - May 1 2016
Externally publishedYes

Keywords

  • calorimetry
  • enthalpy of formation
  • loparite
  • Rare earth perovskites

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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