Dual-mode optical thermometry via efficient Bi3+→Eu3+ energy transfer in CaScAlSiO6 phosphors

Abstract

Accurate and self-referential temperature measurements are crucial for monitoring inaccessible workpieces, hazardous environments, and fluids. In this study, we developed CaScAlSiO₆:Bi³⁺/Eu³⁺, a high-sensitivity, polychromatic, dual-luminescent center optical thermometric material, and investigated its luminescence mechanism through emission spectroscopy and decay lifetime characterization. By adjusting the Bi³⁺ to Eu³⁺ ratio, the samples achieved a visible color transition from blue to pink, revealing a unique energy transfer mechanism between the two luminescent centers that enables tunable emission and enhanced sensitivity. Owing to the unique thermal quenching characteristics of Bi³⁺ and Eu³⁺, the CaScAlSiO₆ samples demonstrated superior optical thermometry capabilities over a temperature range from 323 K to 453 K. At 453 K, the fluorescence intensity ratio between Bi³⁺ and Eu³⁺ reached peak sensitivities, absolute sensitivity (S_a) of 4.11 % K⁻¹ and relative sensitivity (S_r) of 0.87 % K⁻¹. Additionally, these samples exhibited a significant chromatic shift of 0.0508, demonstrating the potential for visual temperature sensing, while consistently showing excellent reversibility and repeatability in performance. The impressive performance of the two temperature measurement systems, characterized by their exceptional results, high sensitivity, and precise signal resolution, positions CaScAlSiO₆:Bi³⁺/Eu³⁺ luminescent materials as a promising candidate for multi-mode and self-referenced luminescent thermometry applications.