Electronic structure and VUV spectroscopy of bismuth-containing phosphate-tungstate crystals

The origin of intrinsic luminescence and mechanisms of excitation energy transfer in undoped K₂Bi(WO₄)(PO₄) and K_6.5Bi_2.5W₄P₆O₃₄ crystals are revealed in complex experimental and computational studies. The photoluminescence (PL) properties are studied under the VUV synchrotron excitations. The electronic structures of the crystals are calculated using the FLAPW method. Calculations indicate different character of the density of electronic states in the lower parts of the Conduction bands of K₂Bi(WO₄)(PO₄) and K_6.5Bi_2.5W₄P₆O₃₄. The PL emission spectra of K₂Bi(WO₄)(PO₄) and K_6.5Bi_2.5W₄P₆O₃₄ reveal wide bands peaking near 540 and 620 nm respectively. The PL in both compounds is effectively excited in 3.7 - 8 eV region of excitation energies.