Energetics of stepwise disordering transformation in pyrochlores, RE 2Ti 2O 7 (RE = Y, Gd and Dy)

Shmuel Hayun, Tien B. Tran, Jie Lian, Antonio F. Fuentes, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

The capacity to incorporate actinide cations makes pyrochlore titanates first-choice phases in titanate-based waste form ceramics. Despite broad interest in the pyrochlore order-disorder transformation due to the cumulative effects of 238U, 235U and 232Th radioactive decay and their daughter products, only limited thermodynamic data, mainly based on simulations of ion-beam irradiation experiments, have been reported. In this work, for the first time, heavily disordered pyrochlores, RE 2Ti 2O 7 (RE = Y, Gd and Dy), from mechanical milling of their constituent oxides, were thermochemically investigated. Two types of thermal events were identified using high-temperature differential scanning calorimetry and correlated to the structural disorder in the cation and anion sublattices. Moreover, the excess formation energy measured by oxide melt solution calorimetry shows that the smaller the ionic radius of the RE, the easier it is to remove damage domains.

Original languageEnglish
Pages (from-to)4303-4310
Number of pages8
JournalActa Materialia
Volume60
Issue number10
DOIs
StatePublished - 1 Jun 2012

Keywords

  • Diffusionless transformation
  • Disordering transformation
  • Formation enthalpy
  • Pyrochlore

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