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

抄録

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°C consisted of Zn₂TiO₄, TiO₂, RE₂Ti₂O₇, and RE₂TiO₅ (RE = Ho³⁺ and/or Yb³⁺) phases. Bright UC emission peaks centered at 542 and 670 nm 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:1TiO₂ doped with 0.05 mol % Ho³⁺, 9 mol % Yb³⁺ fired at 1200°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.