Structural and Luminescence Properties of Li3Y2(BO3)3 Synthesized by Solid-State Reactions

A new binary metal borate compound, trilithium diyttrium orthoborate, Li 3 Y 2 (BO 3 ) 3 was successfully synthesized by a solid-state reaction at 1000°C using the initial reactants of Li 2 CO 3 , Y 2 O 3 , and H 3 BO 3 (mole ratio 1.5:1:3). The phase analysis, crystallinity and size distribution of Li 3 Y 2 (BO 3 ) 3 was investigated by X, ray powder diffraction (XRD) and Scanning Electron Microscopy (SEM). It was found that single phase Li 3 Y 2 (BO 3 ) 3 crystallizes in  orthorhombic crystal system with refined unit cell parameters of a=8.9228, b=9.5840(7), c=20.4469A, Z=9, and represent the space group of Pmmm. Particles size distribution estimated from the SEM images are in the range of 20 to 200 µm. The luminescence properties of Li 3 Y 2 (BO 3 ) 3 were investigated by using steadystate photoluminescence (PL) measurement as a function of temperature. The spectra are dominated by transitions related to defects present in the sample, in the visible region of the spectrum. A relatively low intensity band-to-band transition was also observed at high energy side of the spectrum centered at around 3.33 eV. This peak is decomposed to two close peaks at 3.32 and 3.35 eV using Gauss fitting. From the temperature behavior of peak energies of these emissions, the band gap of Li 3 Y 2 (BO 3 ) 3 is estimated to be 3.35 eV for the first time.