A new disodium hafnium borate Na2Hf(BO3)2: synthesis, crystal structure, DFT calculations and luminescent properties

Abstract

Abstract A ternary borate Na2Hf(BO3)2 has been prepared using a high temperature molten salt method and structurally determined by single crystal X-ray diffraction analysis. It crystallizes in dolomite-type structure with trigonal space group R3̅, and features a layer structure containing [Hf(BO3)2] layers and Na atom layers perpendicular to the c-axis. Band structure calculation using the density functional theory (DFT) method indicates that Na2Hf(BO3)2 has an indirect bond gap of about 4.76 eV. The photoluminescence excitation and emission spectra, decay curve, and the color coordinates of Na2Hf(BO3)2 were investigated. The results show that it can be efficiently excited by UV light (302 nm) and presents blue-green emission (centred at 480 nm), which may be attributed to the lattice defect emission.