Synthesis and upconversion luminescence properties of ZnO-TiO2 containing Ho3+ and Yb3+

Ho3+ and Yb3+ co-doped ZnO-TiO2 composites were prepared by conventional solid-state reaction method and their upconversion (UC) luminescence characteristics were evaluated. The effects of ZnO/TiO2 mixing ratio, and Ho3+ and Yb3+ concentrations were investigated. The ZnO-TiO2 composite products fired at 1200 degrees C consisted of Zn2TiO4, TiO2, RE2Ti2O7, and RE2TiO5 (RE = Ho3+ and/or Yb3+) phases. Bright UC emission peaks centered at 542 and 670nm wavelengths from the Ho3+ ions were observed. The UC emission intensity of the product was changed by varying ZnO/TiO2 mixing ratios, Ho3+ and Yb3+ concentrations. The optimum condition for the brightest UC emission was 1ZnO: 1TiO(2) doped with 0.05 mol% Ho3+, 9 mol% Yb3+ fired at 1200 degrees C for 4 h. The pump power dependent studies demonstrated that UC emissions related to the two-photon process and UC mechanisms were suggested and discussed in detail. (C) 2017 The Ceramic Society of Japan. All rights reserved.