Synthesis and structure of β-Ca3Ga2N4, a ternary nitride with two interpenetrating three dimensional nets

We report the structure of a second polymorph of the ternary calcium gallium nitride Ca3Ga2N4, synthesized as crystals from the elements in sealed niobium tubes at 760 degrees C using a Na/Ca melt as the growth medium. The material is an almost colorless transparent insulator. beta-Ca3Ga2N4 crystallizes in I4(1)/acd (No. 142) with a=b=11.210(1) Angstrom, c=15.914(2) Angstrom and Z=16. It contains a pair of identical, independent interpenetrating networks based on corner sharing GaN4 tetrahedra, which may be designated (3)(infinity)[[Ga4N6]N-4/2] and are related to the (3)(infinity)[[Si]N-4/2] framework in beta-cristobalite. (C) 1998 Elsevier Science S.A.