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 for the first time.•The crystal structures of MgInBO4 and MgIn7/8B7/8O29/8 have been solved and refined from powder X-ray diffraction data.•The possible crystal chemical analysis from MgIn7/8B7/8O29/8 to MgInBO4 is discussed.•Infrared spectra and UV–vis diffuse reflectance spectra of MgInBO4 and MgIn7/8B7/8O29/8 have been measured.

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 °C, belongs to the warwickite family. It crystallizes in the Pnma space group (no. 62) with a=9.5443(1) Å, b=3.2771(1) Å, c=9.5228(1) Å, and Z=4. The fundamental building units are liner –Mg(In)O6–[In(Mg)]2O10–Mg(In)O6– 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 °C. It crystallizes in the P121/n1 space group (no. 14) with a=17.0976(1) Å, b=3.2504(1) Å, c=5.3387(1) Å, β=96.0829(3)°, and Z=4. The structure of MgIn7/8B7/8O29/8 contains [In(2)/Mg(2)]2O10 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 °C and 1180 °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.

Graphical abstractThe structural transformation from the monoclinic MgIn7/8B7/8O29/8 (P121/n1) to the orthorhombic MgInBO4 (Pnma).Figure optionsDownload full-size imageDownload as PowerPoint slide