Fabrication of potassium salts doped zinc tungstates prepared with nitrate, sulfate, chloride and their photoluminescence properties

In this work, we found the significant improvement of photoluminescence of zinc tungstate doped with potassium salts. The samples were prepared by solid-state reaction using ZnO, WO3, KNO3, K2SO4, and KCl as starting powders. The powders were mixed with the molar ratios of ZnO: WO3: potassium salts = 1: 1: x and sintered at 800 °C for 3 h in air. The emission peak of photoluminescence excited at 275 nm was observed at 465 nm. With increasing potassium salts content, the intensity increased reached its maximum at x = 0.02 and decreased. The tendency of the luminescence intensity for KCl doping was almost the same as KNO3 doping, whereas, for K2SO4 doping, the tendency of the decrease was less steep than other doping. The order of each maximum intensity was KNO3>K2SO4>KCl. It was considered that K replacing Zn in the crystal lattice enhanced the intrinsic luminescence in the blue wavelength region. Moreover, different anions doping had the different effect of the enhancement of the luminescence.