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

Abstract A ternary borate Na 2 Hf(BO 3 ) 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 R 3̅, and features a layer structure containing [Hf(BO 3 ) 2 ] layers and Na atom layers perpendicular to the c -axis. Band structure calculation using the density functional theory (DFT) method indicates that Na 2 Hf(BO 3 ) 2 has an indirect bond gap of about 4.76 eV. The photoluminescence excitation and emission spectra, decay curve, and the color coordinates of Na 2 Hf(BO 3 ) 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.