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

This paper reports a new type of PbTiO3:Yb3+/Er3+ (PTO:Yb3+/Er3+) phosphor synthesized by sol-gel method. Under 980 nm excitation, PTO:Yb3+/Er3+ phosphors exhibited green emission bands centered at 524/549 nm (2H11/2/4S3/2 → 4I15/2) and red emissions 661 nm (4F9/2 → 4I15/2). Concentration-dependent upconversion (UC) luminescence spectra showed that the optimal luminescence was observed at 6at%Yb3+/2at%Er3+-codoping concentration. A possible UC mechanism for PTO:Yb3+/Er3+ 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:Yb3+/Er3+ phosphor is a promising candidate for optical temperature sensors with high sensitivity and good repeatability.