Upconversion Luminescence and Temperature Sensing Performance of TiO₂-ZnO:Yb³⁺/Ho³⁺ Phosphors

In this study, TiO₂-ZnO:Yb³⁺/Ho³⁺ upconversion phosphors are synthesized by a solid-phase reaction method and their Yb³⁺ concentration dependence is analyzed. The crystal structure of the phosphors is analyzed by X-ray diffractometry, where each sample is composed of Zn₂TiO₄ and Yb₂Ti₂O₇. Photoluminescence characteristics are analyzed and peaks are observed at wavelengths of 539 nm (⁵F₄, ⁵S₂ → ⁵I₈) and 669 nm (⁵F₅ → ⁵I₈). High intensity luminescence is obtained for samples with Yb = 7–8 mol%. Analysis of temperature characteristics shows absolute and relative sensitivities of 0.0052 K⁻¹ and 0.40% K⁻¹, respectively. The samples are found to be chemically stable, indicating that TiO₂-ZnO:Yb³⁺/Ho³⁺ could be used as a temperature sensor.