High-precision optical thermometry using Pr-doped NaCaY(MoO) luminophores: a multi-spectral and chromaticity-based approach to non-contact temperature sensing.

A series of NaCaY(MoO) (NCYM) phosphors doped with Pr ions was synthesized to develop advanced materials for optical temperature sensing. The structures, morphologies, and luminescent characteristics of these phosphors were thoroughly analyzed. X-ray diffraction (XRD) results confirm that all phosphors exhibit a tetragonal phase with a scheelite-type structure. Optical properties were characterized using UV-visible absorption and photoluminescence (PL) spectroscopy. Under 450 nm excitation, optimal luminescence intensity was achieved at a Pr concentration of 30 mol%. Fluorescence intensity ratio (FIR) techniques, based on emissions from various excited states of Pr (P → H and P → H; P → H and P → F), were employed for thermometric characterization over the 298-498 K range. The results indicate excellent temperature detection performance, with maximum relative sensitivities of 0.69% per K and 1.2% per K at 298 K, respectively. Additionally, a study of temperature uncertainty (δ) demonstrated values below 0.06 K, with repeatability () exceeding 97%. The temperature-induced shift in chromaticity further improves the material's functionality, as the CIE coordinates change from (0.3806, 0.4278) at 298 K to (0.3772, 0.4229) at 498 K, demonstrating a stable transition towards yellow. These findings suggest that Pr-activated NCYM phosphors have significant potential for application in non-contact optical thermometry.