New Compounds with a Ca_3Ga_2Ge_4O_(14) Structure: Ln_3Ga_3Ge_2BeO_(14) (Ln = La-Eu)

摘要

The compounds Ln_3Ga_3Ge_2BeO_(14) (Ln = La-Eu) with a Ca_3Ga_2Ge_4O_(14) structure were prepared by solid-phase reactions at 1250-1350 deg C. An extension of isomorphism limits in relation to Ln, compared to those for Ln_3Ga_5MO_(14) (Ln = La-Nd; M = Si, Ge), is a result of a decrease in the Ln_3Ga_5O_(12) garnet phase stability upon an increase in the La : Ga ratio. The new compounds possess a wide homogeneity field: in the La_3Ga_(5-2x)Ge_xBe_xO_(14) system, 0 <= x <= 1.8. Be~(2+) ions occupy tetrahedral 2d sites in a disordered structure.