Self-calibrated optical thermometer based on luminescence from SrLu₂O₄:Bi³⁺,Eu³⁺ phosphors

Bi³⁺,Eu³⁺ co-doped SrLu₂O₄ phosphors were synthesized by a solid state reaction method. Their structural, luminescent and temperature sensing properties have been systematically investigated. The color-tunable emissions from violet to red were detected with the increase of Eu³⁺ concentration. Relying on energy transfer process from Bi³⁺ to Eu³⁺ and thermal quenching behaviour, the fluorescence intensity ratio (FIR) presents excellent temperature sensing performance. The maximum absolute and relative sensitivities reach 1.10% K^-1 and 0.87% K^-1, respectively. These meaningful results indicate that SrLu₂O₄:Bi³⁺,Eu³⁺ is a promising material for optical temperature sensing.