Two new alkaline-earth-oxoindates: BaCa2In6O12 and BaSr2In6O12

The hitherto unknown compounds (I): BaCa2In6O12 and (II): BaSr2In6O12 were prepared and examined by single crystal X-ray work. (I) and (II) crystallize with hexagonal symmetry, space group C6h2-P63/m, with (I): a = 9.880, c = 3.211 A; (II): a = 9.9443; c = 3.2671 A, Z = 1. Both compounds are isotypic to the metastable oxides AM2Ln6O12, but without metastable behavior. The [In6O12]6- network is occupied by the alkaline earth ions. One of the tunnels is stuffed by Ca2+ and Sr2+, respectively, the other one by Ba2+ in a statistical distribution on possible point positions. (I) and (II) prove the existence of the AM2Ln6O12-type in respect to small Ln3+ ions. (author)