Color-tunable emissions in Bi3+/Eu3+ activated phosphors for multi-mode optical thermometers

Accurate, self-referential temperature measurements of inaccessible workpieces, bodies in hazardous work environments, or fluids are of tremendous significance. Here, a series of Ca3Y2Ge3O12(CaYGO):1.0%Bi3+/yEu3+ phosphors were manufactured, which simultaneously presents the characteristic radiation of dopant ions, and the luminescence mechanism was investigated via emission spectroscopy and decay lifetime characterization. Upon excitation at 285 nm, energy transfer (Bi3+ → Eu3+) of the as-prepared materials exhibited adjustable polychromatic emissions (blue → red). The temperature dependence was evaluated via thermal quenching. The CaYGO phosphors demonstrated a high relative sensitivity of 0.019 K−1 at 297.8 K according to FIR (the fluorescence intensity ratio) operation rules. Furthermore, temperature-controlled emission spectroscopy displayed a significant chromaticity shift (Δs = 0.05679 for 297.8–480 K). The temperature-dependent lifetime of Eu3+ which regarded as a basis of the self-reference measurement provided the maximum relative sensitivity was 0.038%. The excellent signal resolution, high sensitivity values, and results produced by three temperature measurement systems revealed that Ca3Y2Ge3O12: Bi3+/Eu3+ luminescent materials have excellent development prospects in multi-mode and self-referenced luminous thermometry fields.