Monoclinic SmAl3(BO3)4: synthesis, structural and spectroscopic properties

Abstract

The SmAl3(BO3)4 single crystals are synthesized by the group growth on seeds method, and its crystal structure was solved from single crystal experiment and purity of the bulk material was proved by Rietveld method. This borate crystallizes in the monoclinic space group C2/c with cell parameters a = 7.2386 (3) Å, b = 9.3412 (5) Å, c = 11.1013 (4) Å, β = 103.2240 (10) °. The Infrared and Raman spectroscopy confirmed the monoclinic structure of SmAl3(BO3)4. Under the 532.1 nm excitation, luminescence spectra exhibit bands assignable to the transitions from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2. Similarity of luminescence spectra of trigonal and monoclinic polymorphs is explained by the minor role of Sm-O bond distortion and primary role of rotation distortion of SmO6 octahedra. Smaller covalency of Sm-O bond in alumoborates is deduced in comparison with galloborates. Calorimetric measurements did not reveal high-temperature structural phase transitions up to 720 K.