Synthesis and crystal structure of a novel ludwigite borate: Mg2InBO5

A novel ludwigite borate Mg2InBO5 has been synthesized by solid-state reaction. Its crystal structure was solved by program Jana2006 from powder X-ray diffraction data, and then refined using Rietveld method. It crystallizes in the Pbam space group (No. 55) with a = 12.54806(8) angstrom, b = 9.46943(6) angstrom, c = 3.13855(2) angstrom, V = 372.932(4) angstrom(3), and Z = 4. The disorder of Mg and In atoms exists in Mg2InBO5. The In atoms prefer to occupy the M1 and M2 site, while Mg atoms tend to occupy the M3 and M4 sites, which is in agreement well with the cation distributions in the ludwigite family. The crystal structure of Mg2InBO5 is built from Mg/InO6 octahedra and trigonal BO3 groups stacking layer upon layer along the c-axis. The Mg/InO6 octahedra connect each other by sharing edges to form two flat walls along the c-axis in the sequence M3-M2-M3 and M1-M4-M1. The trigonal BO3 group in Mg2InBO5 was confirmed by infrared absorption spectrum, and UV-Vis diffuse reflectance spectrum of Mg2InBO5 has been measured. The structure characteristics of the ludwigite family were reviewed, with a possible rule proposed. (c) 2013 Elsevier B.V. All rights reserved.