High-precision optical thermometry using Pr ³⁺ -doped NaCaY(MoO ₄ ) ₃ luminophores: a multi-spectral and chromaticity-based approach to non-contact temperature sensing

Abstract

A series of NaCaY(MoO₄)₃ (NCYM) phosphors doped with Pr³⁺ 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 Pr³⁺ concentration of 30 mol%. Fluorescence intensity ratio (FIR) techniques, based on emissions from various excited states of Pr³⁺ (³P₁ → ³H₅ and ³P₀ → ³H₅; ³P₁ → ³H₅ and ³P₀ → ³F₂), 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<i>T</i>) demonstrated values below 0.06 K, with repeatability (<i>R</i>) 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 Pr³⁺-activated NCYM phosphors have significant potential for application in non-contact optical thermometry.