Temperature and concentration effects on upconversion photoluminescence properties of Ho³⁺ and Yb³⁺ codoped 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ multifunctional ceramics

Ho³⁺ and Yb³⁺ codoped lead magnesium niobate-lead titanate (PMN-PT) ceramics with various doping concentration have been fabricated by conventional solid reaction method. Under the excitation of 980 nm laser, as-synthesized samples exhibit bright yellow-green upconversion (UC) luminescence. Their UC photoluminescence properties were investigated by the emission spectra with respect to various concentration of Ho³⁺ and Yb³⁺. Results show that optimal luminescent concentration was obtained in 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ ceramics codoped with 0.5 mol% Ho³⁺ and 2 mol% Yb³⁺ (abbreviated as 67PMN-33PT:2Yb,0.5Ho). The possible mechanism of UC emission was discussed by energy level diagrams of Ho³⁺ and Yb³⁺ ions according to the dependence of integrated intensity of UC emission bands on pumping power. Furthermore, the temperature dependence of UC emission intensity of 67PMN-33PT:2Yb,0.5Ho sample was investigated in detail in the range of 25-180 °C under excitation by a 980 diode laser. According to Arrhenius formula, the fitting result of the effect of temperature on integrated intensity of emission band was coinciding well with the experiment results. It is shown that the emission intensity depends strongly on temperature, which has excellent relative sensitivity with its maximum value of 0.77% K^-1 at 93 °C. These indicate that the 67PMN-33PT:2Yb,0.5Ho ceramic may be useful for temperature sensing and optical-electrical devices as a multifunctional material.