Synthesis and crystal structure of Ln2M2+Ge4O12, Ln=rare-earth element or Y; M=Ca, Mn, Zn

The crystal structure of the promising optical materials Ln2M2+Ge4O12, where Ln=rare-earth element or Y; M=Ca, Mn, Zn and their solid solutions has been studied in detail. The tendency of rare-earth elements to occupy six- or eight-coordinated sites upon iso- and heterovalent substitution has been studied for the Y2−xErxCaGe4O12 (x=0–2), Y2−2xCexCa1+xGe4O12 (x=0–1), Y2Ca1−xMnxGe4O12 (x=0–1) and Y2−xPrxMnGe4O12 (x=0–0.5) solid solutions. A complex heterovalent state of Eu and Mn in Eu2MnGe4O12 has been found.