Designing dual mode of non-contact optical thermometers in double perovskite Ca2LaTaO6:Bi3+, Eu3+ phosphors

Optical performance for rigorous non-contact temperature measurement needs to overcome the disadvantages of low sensitivity and poor signal discriminability. In this work, Bi3+ and Eu3+ co-doped Ca2LaTaO6 (CLTO) phosphors were synthesized by a solid phase method. The crystal structures of the cations in various coordination environments were confirmed by means of XRD, XPS, and DRS. Using SEM and TEM techniques, the morphology of the samples was investigated in detail. Furthermore, the occupancy of the two luminescent centers of Bi3+ was analyzed in detail based on the luminescence properties of the CLTO:Bi3+ phosphor. Additionally, dipole–dipole interaction contributes to the energy transfer from Bi3+ to Eu3+ ions in the CLTO host, and the transfer efficiency is as high as 100%. Finally, given the different responses of Bi3+ and Eu3+ to temperature, a dual-mode optical thermometer was designed. Based on FIR technology, the maximum Sa and Sr values are 0.041 K-1 and 0.76% K−1, respectively. Also, the maximum value of Sr of the Bi3+ temperature-dependent lifetime is 1.04%K−1 at 293 K. These results indicate that the designed dual-mode optical thermometers of CLTO:Bi3+,Eu3+ have great potential in temperature measurement.