High-pressure synthesis of SmGe₃

Abstract

The new samarium germanide SmGe3 is obtained by high-pressure high-temperature synthesis of pre-reacted mixtures of samarium and germanium at a pressure of 9.5 GPa and temperatures between 1073 and 1273 K. SmGe3 decomposes at 470(5) K into SmGe2, α-Sm3Ge5 and a hitherto unknown phase. SmGe3 exhibits a superstructure of the cubic Cu3Au-type. Transmission electron microscopy measurements of crystalline particles and prepared lamellae indicate a high density of defects on the nanoscale. Selected area electron diffraction and elaborate X-ray powder diffraction measurements consistently indicate a 2a0 × 2a0 × 2a0 superstructure adopting space group $Fm\overline{3}m$ with a = 8.6719(2) Å.

Stabilization of CeGe$_3$ with Ti and O featuring tetravalent Ce ions: (Ce$_{0.85}$Ti$_{0.15}$)Ge$_3$O$_{0.5}$

“…It crystallized in a cubic Cu 3 Au-type structure with a = 4.354(4) A, isotypic with CeSn 3 and CePb 3 . The specific atomic volume (unit cell volume / total number of atoms in unit cell) is 20.635 A 3 , which is similar to the newly discovered cubic Cu 3 Au-type SmGe 3 that is also synthesized under high pressure with a specific atomic volume of 20.38 A 3 [18]. The high pressure and high temperature synthesis (3 ∼ 12 GPa, 500 ∼ 1200 °C) of LaGe 3 lead to the formation of a compound with a BaPb 3 -type instead of Cu 3 Au-type structure [19] with specific atomic volume of 21.78 A 3 , larger than hp-CeGe 3 .…”