Dual-mode optical thermometry based on Bi3+/Eu3+ co-activated BaGd2O4 phosphor with high sensitivity and signal discriminability

A series of BaGd2O4:Bi3+,Eu3+ phosphors with dual-emitting centers were prepared by high-temperature solid-state method. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), fluorescence spectroscopy, lifetime decay curve and variable temperature emission spectroscopy were used to systematically study the structure, luminescence performance and temperature characteristics. Under ultraviolet (UV) excitation, the BaGd2O4:Bi3+,Eu3+ phosphor showed a broad-band emission in the blue region corresponding to transitions of Bi3+ ions and the sharp red light emission corresponding to Eu3+ ions. The Bi3+ and Eu3+ ion emission peaks were well-separated, which meets a prerequisite for efficient temperature signal resolution measurement. The fluorescence intensity ratio (FIR) technique was used to measure the different temperature response characteristics between Bi3+ blue emission and Eu3+ red emission. When the temperature varies from 293 K to 473 K, the relative temperature sensitivity (Sr) of BaGd2O4:Bi3+,Eu3+ phosphors is obtained, was determined as 1.0182%K−1. In addition to calculating the relative sensitivity by FIR technology, we can also obtain the value of Sr through experiments and formulas related to the decay life, and found to be 1.0651%K−1. Therefore, BaGd2O4: Bi3+,Eu3+ phosphor is an excellent non-contact optical temperature measurement material.