Synthesis and Structures of [Sr2−xEux]IrH5, [Sr2−xEux]RhH5, [Ca2−xEux]IrH5, and Eu2RhH5

Abstract

Samples of various compositions of [Sr2−xEux]MH whereM= Rh or Ir and [Ca2−xEux]IrH5were synthesized from stoichiometric mixtures of EuH2, SrH2, or CaH2, and Rh or Ir powders in a hydrogen atmosphere at 700°C. Powder X-ray diffraction data of the black single-phase products were indexed on the basis of a face-centered cubic lattice. The variations in the unit cell parameters as a function ofxwere consistent with Vegard's Rule for 0 ≤x≤ 2 range. The unit cell parameters increased with decreasingxbetween the limits of 7.580 and 7.651 Å for [Sr2−xEux]IrH5and between the limits of 7.557 and approximately 7.60 A° for [Sr2−xEux]RhH5. Unit cell parameters increased from 7.297 to 7.580 Å asxwent from 0.25 to 2 for [Ca2−xEux]IrH5. The estimated standard deviation for the unit cell parameters is 0.001 Å. The crystal structures belonged to theFm3m(No. 225) space group with random occupancy of Sr or Ca and Eu in the 8csites, Rh or Ir ions located at the 4asites, and H in the 24esites. The formation of Eu2RhH5is also reported. The X-ray diffraction data for this new ternary hydride were indexed FCC with the cell length equal to 7.555 Å.