Crystal structures of two novel borate compounds MgInBO4 and MgIn7/8B7/8O29/8

Two novel borate compounds MgInBO4 and MgIn7/8B7/8O29/(8), have been synthesized via solid-state reactions, and their crystal structures have been solved and refined from powder X-ray diffraction data. The compound MgInBO4, which was obtained at 1190 degrees C, belongs to the warwickite family. It crystallizes in the Pnma space group (no. 62) with a=9.5443(1) angstrom, b=3.2771(1) angstrom, c=9.5228(1) angstrom, and Z=4. The fundamental building units are liner -Mg(In)O-6-[In(Mg)](2)O-10-Mg(In)O-6- chains and isolated BO3 triangles. The low-temperature phase, MgIn7/8B7/8O29/8, whose crystal structure is solved ab initio by the charge-flipping method with standard chemical formula MgInBO4, was prepared at 1080 degrees C. It crystallizes in the P12(1)/n1 space group (no. 14) with a=17.0976(1) angstrom, b=3.2504(1) angstrom, c=5.3387(1) angstrom, beta=96.0829(3)degrees, and Z=4. The structure of MgIn7/8B7/8O29/8 contains[In(2)/Mg(2)](2)O-10 groups, -MgO6-InO6- infinite ribbons and isolated BO3 triangles. The experiments and the differential thermal analysis (DTA) show the decompositions of MgInBO4 and MgIn7/8B7/8O29/8 happen at about 1220 degrees C and 1180 degrees C, respectively. The comparative crystal chemistry from MgIn7/8B7/8O29/8 to MgInBO4 has been discussed. Infrared spectra and UV-vis diffuse reflectance spectra of MgInBO4 and MgIn7/8B7/8O29/8 were measured. (C) 2013 Elsevier Inc. All rights reserved.