Heat capacities, standard entropies and Gibbs energies of Sr-, Rb- and Cs-substituted barium aluminotitanate hollandites

Lili Wu, Jacob Schliesser, Brian F. Woodfield, Hongwu Xu, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Heat capacities of Sr-, Rb-, and Cs-hollandite with the compositions Ba1.14Sr0.10Al2.38Ti5.59O16, Ba1.17Rb0.19Al2.46Ti5.53O16, and Ba1.18Cs0.21Al2.44Ti5.53O16 were measured from T = (2 to 300) K using a Quantum Design Physical Property Measurement System (PPMS). From the heat capacity results, the following thermodynamic parameters have been determined. The characteristic Debye temperatures ΘD over the temperature range (30 to 300) K of Sr-, Rb-, and Cs-hollandite are T = (178.2, 189.7, and 189.2) K, respectively, and their standard entropies at T = 298.15 K are (413.9 ± 8.3), (415.1 ± 8.3), and (419.6 ± 8.4) J · K-1 · mol-1. Combined with previously reported formation enthalpies, their corresponding Gibbs energies of formation from oxides (ΔfGox°) are (-194.9 ± 11.4), (-195.0 ± 12.8), and (-201.1 ± 12.8) kJ · mol-1, and those from elements (ΔfGel°) are (-7694.6 ± 12.5), (-7697.0 ± 13.9), and (-7697.1 ± 13.9) kJ · mol-1 at T = 298.15 K. The similarities among the obtained ΔfGox° values suggest that the three substituted hollandites have similar thermodynamic stabilities at standard conditions, which is in agreement with the ease of Cs-Rb-Sr substitutions in the hollandite structure.

Original languageEnglish (US)
Pages (from-to)1-7
Number of pages7
JournalJournal of Chemical Thermodynamics
Volume93
DOIs
StatePublished - Feb 1 2016
Externally publishedYes

Keywords

  • Entropy
  • Gibbs energy
  • Heat capacity
  • Hollandite
  • Radionuclide immobilization

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)
  • Physical and Theoretical Chemistry

Fingerprint Dive into the research topics of 'Heat capacities, standard entropies and Gibbs energies of Sr-, Rb- and Cs-substituted barium aluminotitanate hollandites'. Together they form a unique fingerprint.

Cite this