Fluorite and pyrochlore phases in the HfO2 -La2O 3 -Gd2O3 systems: Characterization and calorimetric study of samples quenched from melts formed by laser heating and aerodynamic levitation

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

New experimental results on pyrochlore and defect fluorite phases in HfO2-La2O3 and HfO2-Gd 2O3 systems are summarized. Fluorite Hf 0.5Gd0.5O1.75 was formed by containerless melting and quenching. Melts with 25-65 mol% La2O3 did not produce any fluorite-type phases, but pyrochlores with cell parameters 10.74 to 10.86 Å. The fluorite phase of Hf0.5La0.5O 1.75 can be formed on crystallization of an amorphous precursor from aqueous precipitation. Both La- and Gd- fluorite phases transform to ordered pyrochlore on annealing at 1450°C. The enthalpies of formation from oxides are -107 ±5 kJ/mol for Hf2La2O7 and -49 ±5 kJ/mol for Hf2Gd2O7 as measured by high-temperature solution calorimetry. Further experiments are needed to elucidate the nature of stabilization of fluorite phase in thin films and powders. Occurrence of disordered phases in thin films, nanoparticles and radiation damaged materials is discussed.

Original languageEnglish (US)
Title of host publicationStructure/Property Relationships in Fluorite-Derivative Compounds
PublisherMaterials Research Society
Pages12-17
Number of pages6
ISBN (Print)9781615677627
DOIs
StatePublished - 2008
Externally publishedYes
Event2008 MRS Fall Meeting - Boston, MA, United States
Duration: Dec 1 2008Dec 5 2008

Publication series

NameMaterials Research Society Symposium Proceedings
Volume1122
ISSN (Print)0272-9172

Conference

Conference2008 MRS Fall Meeting
CountryUnited States
CityBoston, MA
Period12/1/0812/5/08

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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