Optical High Temperature Sensor Based on Enhanced Green Upconversion Emissions in Er(3+)-Yb(3+)-Li(+) Codoped TiO(2) Powders

The Er(3+)-Yb(3+)-Li(+) codoped TiO(2) powders have been prepared by sol-gel method. The strong enhancement of green and red upconversion emissions were obtained for Er(3+)-Yb(3+) codoped TiO(2) by additional Li(+) codoping and investigated using 976 nm semiconductor laser diode excitation. The enhanced upconversion emissions by the addition of Li(+) resulted from the formation of Li compound with lower crystal field symmetry. The fluorescence intensity ratio (FIR) of green upconversion emissions from the transitions of (2)H(11/2) > 4I(15/2) and (4)S(3/2) -> (4)I(15/2) of Era in the Er(3+)-Yb(3+)-Li(+) codoped TiO2 has been studied as a function of temperature in the range of 300-925 K, and the maximum sensitivity was determined to be 0.0025 K(-1). Er(3+)-Yb(3+)-Li(+) codoped TiO(2) material with the highest operating temperature up to 925 K, has higher temperature sensitivity and fluorescence efficiency being a promising candidate for applications in optical high temperature sensor.