Syntheses and characterization of two alkaline and transition metal orthoborates, LiMBO3 (M = Zn, Cd)

Two alkaline and transition metal orthoborates, LiMBO3 (M = Zn, Cd), have been synthesized and their crystal structures determined by single-crystal XRD methods with the following crystal data: LiZnBO3, P (1) over bar (No. 2), a = 5.0559 (15) angstrom, b = 6.097 (2) angstrom, c = 8.0359 (18) angstrom, alpha = 75.75 (2)degrees, beta = 89.86 (2)degrees, gamma = 89.79 (3)degrees, Z = 4; LiCdBO3, P2(1)/c (No. 14), a = 10.4159 (14) angstrom, b = 9.005 (2) angstrom, c = 10.756 (2) angstrom, beta = 92.521 (13)degrees, Z = 16. The crystal structure of LiZnBO3 is composed of edge-sharing ZnO5 trigonal bipyramids which are bound together via ZnO4 tetrahedra and BO3 planar triangles to form a polyanionic framework. LiCdBO3 also features a 3D framework, but constructed by edge-sharing CdO5 trigonal bipyramids and BO3 tri-angles. Both structures afford open channels that are occupied by Li+ cations. IR spectra further confirm that these two compounds contain the planar triangular BO3 groups. UV-VIS diffuse reflectance spectra show band gaps of about 3.10 and 4.28 eV and solid-state fluorescence spectra demonstrate emission bands at around 542 and 412 nm for LiZnBO3 and LiCdBO3, respectively. Band structure calculations by the density functional theory method indicate that both compounds are direct band-gap insulators. (C) 2015 Elsevier Masson SAS. All rights reserved.