A new diphosphate Li2Na2P2O7: Synthesis, crystal structure, electronic structure and luminescent properties

For the first time, a mixed-alkali diphosphate, Li2Na2P2O7, has been successfully obtained by high-temperature solution growth (HTSG) method. Single crystal X-ray diffraction analysis reveals that it contains anionic [Li2P2O7](infinity) network and 1D [Na](infinity) infinite chains, which are both running along the c-axis. Band structure calculations by density functional theory (DFT) method indicate that Li2Na2P2O7 has an indirect band gap of about 4.88 eV. Moreover, 1 mol% Eu3+ doped Li2Na2P2O7 phosphor was synthesized and its photoluminescence properties were investigated. Under near ultraviolet (NUV) excitation (394 nm), Li2Na2P2O7:0.01 Eu3+ phosphor exhibits a series of emission peaks corresponding to the D-5(0)-> F-7(J) (J = 0, 1, 2, 3, 4) transitions of Eu3+ ion with the CIE chromaticity coordinates of (0.599, 0.375).