Normal and inverse garnets: Ca3Fe2Ge3O12, Ca3Y2Ge3O12and Mg3Y2Ge3O12

The structures of three garnets, namely, tricalcium diiron(III) trigermanium dodecaoxide, tricalcium diyttrium trigermanium dodecaoxide and trimagnesium diyttrium trigermanium dodecaoxide, have been determined by X-ray diffraction using flux-grown single crystals. The cation distributions correspond to a normal garnet structure for Ca 3 [8] Fe 2 [6] Ge 3 [4] O 12 and Ca 3 [8] Y 2 [6] Ge 3 [4] O 12 , and to an inverse garnet structure for (MgY 2 ) [8] Mg 2 [6] Ge 3 [4] O 12 .