高温高圧下でのZintl相シリサイドBaSi₂の構造相転移とSiクラスレートBa₈Si₄₆の生成

抄録

  This article reviews structural phase transitions of Zintl-phase silicide BaSi₂ at high pressures and high temperatures and a formation of Si clathrate Ba₈Si₄₆ from an 8:30 molar mixture of BaSi₂ and Si at high pressures and high temperatures. At pressures ranging from 0 to 10 GPa and temperatures ranging from 300 to 1300 K, BaSi₂ has four phases: BaSi₂ phase, EuGe₂ phase, SrSi₂ phase, and BaSi₂-IV phase. When heated at approximately 5 GPa, BaSi₂ undergoes the three structural phase transitions: the BaSi₂-to-EuGe₂, the EuGe₂-to-SrSi₂, and the SrSi₂-to-BaSi₂-IV transitions. At 4.3 GPa, Ba₈Si₄₆ is formed by a solid state reaction of an 8:30 molar mixture of SrSi₂-phase BaSi₂ and Si after BaSi₂ undergoes the BaSi₂-to-EuGe₂ and the EuGe₂-to-SrSi₂ transitions. The structural phase transitions of BaSi₂ and formation process of Ba₈Si₄₆ are discussed comparing it with structural phase transitions of SrSi₂ and of an 8:30 mixture of SrSi₂-pahse SrSi₂ and Si.