Investigation of the structural and luminessence properties of Li3Y2(BO3)3 synthesized by solid-state reactions

Abstract

A new binary metal borate compound, trilithiumdiyttriumorthoborate, Li3Y2(BO3)3 was successfully synthesized by a solid-state reaction at 1000 °C using the initial reactants of Li2CO3, Y2O3, and H3BO3 (molar ratio in the order; 1.5:1:3). The phase, crystallinity and size distribution of Li3Y2(BO3)3 was investigated by X-Ray Powder Diffraction (XRD) and Scanning Electron Microscopy (SEM). It was found that single phase Li3Y2(BO3)3 crystallizes in orthorhombic crystal with refined unit cell parameters of a=8.9228, b=9.5840, c=20.4469Å, Z=9 and represent the space group of Pmmm. Average particle size was calculated as 70 nm by Scherrer’s equation. The luminescence properties of Li3Y2(BO3)3 were investigated by using steady state photoluminescence (PL) measurement as a function of temperature between 10 to 300 K. It was observed that the spectra are dominated with the transitions in the visible part of spectrum related to defects present in compound. A relatively low intensity band-to-band transition was also observed at high energy side of the spectrum centred at around 3.33 eV. This peak was decomposed into two close peaks at 3.32 and 3.35 eV using Gaussian fitting. From the temperature behaviour of peak energies of these emissions, the band gap of Li3Y2(BO3)3 was estimated to be 3.35 eV for the first time.