Design of white-emitting optical temperature sensor based on energy transfer in a Bi3+, Eu3+ and Tb3+ doped YBO3 crystal

Abstract

Phosphors for remote optical determination have gained great attention for their promising applications, due to their advantageous rapid and noninvasive detection compared to traditional thermometers. In this work, a novel white-emitting optical temperature sensor based on energy transfer in a Bi³⁺, Eu³⁺ and Tb³⁺ doped YBO₃ crystal was designed. By making full use of the crystal structure information and an energy transfer strategy, we obtained a series of wide range color tunable phosphors including one with white emission, which makes it a candidate to replace phosphors for white light emitting diodes (WLEDs). The temperature sensitive energy transfer from the host and Bi³⁺ to Eu³⁺ and Tb³⁺ has been demonstrated by analyzing the spectra from phosphors with different concentrations of the doping ions, in which Bi³⁺ acts as both the emission center and sensitizer. By investigating the temperature-dependent emission of the white light emitting phosphor YBO₃:0.04Bi³⁺,0.003Eu³⁺,0.008Tb³⁺, the absolute sensitivity value (S_a) and relative sensitivity value (S_r) were calculated in different temperature ranges of 200 to 300 K and 298 to 473 K, in which the maximum value of S_r reaches 0.57% K⁻¹ at 398 K. Although the S_r values are not high enough for practical application, our design concept may provide a new perspective for developing novel multifunctional phosphors used as optical temperature sensors and WLED phosphors.