Crystal chemistry of Eu-bearing tuite synthesized at high-pressure and high-temperature conditions

Shuangmeng Zhai, Hexiong Yang, Weihong Xue, Eugene Huang, Daisuke Yamazaki, Shaunna M. Morrison, Robert T. Downs

Research output: Contribution to journalArticlepeer-review


Tuite, γ-Ca 3 (PO 4 ) 2 , is a potential host for rare-earth elements in the deep mantle. Eu-bearing tuite single crystals with chemical formulas of Ca 2.93 Eu 0.04 (PO 4 ) 2 and Ca 2.88 Eu 0.07 Na 0.06 (PO 4 ) 2 were synthesized at 16 GPa and 1600 °C, and their structures were investigated at room temperature with single-crystal X-ray diffraction. The structure refinements of Eu-bearing tuite indicate the preference of Eu 3+ for the smaller 6-coordinated Ca1 site with a coupled vacancy due to the substitution of 2Eu 3+ + □ → 3 Ca 2+ . In NaEu-bearing tuite, both Eu 3+ and Na + occupy the smaller 6-coordinated Ca1 site according to the coupled substitution of Eu 3+ + Na + → 2 Ca 2+ . The presence of Na results in more Eu 2 O 3 in NaEu-bearing tuite, because the coupled substitution is energetically more favorable. REE-bearing tuite could be found on the Moon and the deep Earth’s mantle as a consequence of REE-bearing apatite or/and merrillite transformation under high-pressure and high-temperature conditions.

Original languageEnglish
Pages (from-to)157-163
Number of pages7
JournalPhysics and Chemistry of Minerals
Issue number2
Publication statusPublished - Feb 5 2019


  • Crystal structure
  • Eu-bearing
  • Single-crystal X-ray diffraction
  • Tuite
  • γ-Ca (PO )

ASJC Scopus subject areas

  • General Materials Science
  • Geochemistry and Petrology


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