Wide-Temperature-Range Optical Thermometry Based on Yb3+,Er3+:CaYAlO4 Phosphor

In order to meet the demand for new optical temperature-sensing materials with high sensitivity and a wide application temperature range, Yb3+/Er3+: CaYAlO4 phosphor with excellent physical and chemical stability and thermal conductivity was studied for the first time. Yb3+/Er3+: CaYAlO4 phosphors have been synthesized by the high-temperature solid-state method. Under 980 nm excitation, three characteristic emission bands peaking at 528, 549 and 665 nm were observed which are attributed to the transitions 2H11/2, 4S3/2 and 4F9/2 to 4I15/2, respectively. The temperature-sensing behaviors of the phosphor were investigated using the luminescence intensity ratio technique based on both the TCL (2H11/2/4S3/2) and NTCL (4F9/2/4S3/2, 2H11/2/4F9/2) model over a wide temperature range of 163–700 K. The maximum relative sensitivities of TCLs (2H11/2/4S3/2), NTCLs (4F9/2/4S3/2) and NTCLs (2H11/2/4F9/2) were 3.69% K−1, 0.443% K−1 and 3.86% K−1 at 163 K, 275 K and 163 K, while the maximum absolute sensitivities were 4.04 × 10−3 K−1, 15.2 × 10−3 K−1 and 7.81 × 10−4 K−1 at 499 K, 499 K and 247 K, respectively. Results suggest that Yb3+/Er3+: CaYAlO4 phosphor is a promising temperature-measuring material with advanced optical sensing capabilities over a wide temperature range.