Photochromic and temperature sensing properties of Ho3+-Yb3+ codoped Bi0.495-xNa0.5TiO3 ceramics

With the development of modern industry and people's daily life, more and more smart materials with multifunction are required. In this study, multifunction material Bi0.495-xNa0.5TiO3:0.005Ho-xYb (x = 0.005, 0.010, 0.015, 0.020, 0.025, abbreviated as NBT:Ho-xYb) ceramics have been synthesized. The basic microstructure, upconversion luminescence, photochromic (PC) reaction, and temperature sensing properties of the ceramics have been systematically investigated. It is found that all the ceramics exhibit strong UC emissions, and the UC luminescence intensity depends on the Yb3+ doping content. An optimized UC emission is achieved at x = 0.015. Additionally, all the ceramics show an evident color change after 405-nm irradiation. Based on the PC reaction, a reversible UC luminescence modification can be achieved by alternating light irradiation (405 nm) and thermal stimulus at 230 degrees C, and the luminescence modulation is intensively dependent on the Yb3+ content and emission wavelength. Furthermore, the temperature sensing properties of NBT:Ho-0.015 Yb ceramics at low temperature have been investigated, illustrating a maximal sensitivity of 0.0029 K-1 at 93 K.