The existence and stability of Ca6Zr19O44 compound in the system ZrO2CaO

J. R. Hellmann, V. S. Stubican

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The development of ordered phases in the system ZrO2CaO was studied during prolonged heating of reactive powders derived from gels. The pure phase f{cyrillic}2 was obtained at 1250°C only with gels containing 24 m/o CaO which indicates that the correct composition of this phase is Ca6Zr19O44. This phase has rhombohedral symmetry, space group R3c, and is analogous to the f{cyrillic}2 phase in the HfO2CaO system. The pure phase f{cyrillic}1 (CaZr4O9) was obtained by heating gels containing 20 m/o CaO at 1180°C. This phase often appears as a precursor to the formation of the f{cyrillic}2 phase. At 1355±15°C the f{cyrillic}2 phase decomposes to a cubic ZrO2 solid solution and CaZrO3. At 1235±15°C the f{cyrillic}1 phase decomposes to a cubic ZrO2 solid solution and the phase f{cyrillic}2. The inability to synthesize a phase analogous to the phase f{cyrillic} (Ca2Hf7O16) in the HfO2CaO system can be explained by the low cation diffusivity in the ZrO2CaO system below 1150°C.

Original languageEnglish (US)
Pages (from-to)459-465
Number of pages7
JournalMaterials Research Bulletin
Issue number4
StatePublished - Apr 1982

All Science Journal Classification (ASJC) codes

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

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