Sol-gel synthesis and optical temperature sensing properties of PbTiO3:Yb3+/Er3+ phosphors

This paper reports a new type of PbTiO 3 :Yb 3+ /Er 3+ (PTO:Yb 3+ /Er 3+ ) phosphor synthesized by sol-gel method. Under 980 nm excitation, PTO:Yb 3+ /Er 3+ phosphors exhibited green emission bands centered at 524/549 nm ( 2 H 11/2 / 4 S 3/2  →  4 I 15/2 ) and red emissions 661 nm ( 4 F 9/2  →  4 I 15/2 ). Concentration-dependent upconversion (UC) luminescence spectra showed that the optimal luminescence was observed at 6at%Yb 3+ /2at%Er 3+ -codoping concentration. A possible UC mechanism for PTO:Yb 3+ /Er 3+ phosphor is discussed by the pump power-dependent UC luminescence spectra. The temperature-dependence (298–548 K) of the fluorescence intensity ratios (FIR) for the two green UC emission bands peaked at 524 and 549 nm was studied under a 980 nm laser excitation and the maximum relative sensitivity was approximately 12.25 × 10 −3  K −1  at 298 K. The thermal quenching activation energy of near-infrared (NIR) luminescence was studied. It can be found that the phosphor has a small thermal quenching possibility and excellent thermal stability. The value of repeatability (R) more than 98% has obtained via four cycles of cooling and heating, which prove that the phosphor has a good cycling stability. These results indicate that PTO:Yb 3+ /Er 3+ phosphor is a promising candidate for optical temperature sensors with high sensitivity and good repeatability.