Charge compensation boosts luminous efficiency to achieve ultra-low doped optical thermometer CaWO4: Tb3+ phosphors

Abstract

Optical temperature measurement is crucial in various fields, driving the development of fluorescent thermometer materials that are highly sensitive, environmentally friendly, and cost-effective. This paper investigates a temperature sensitive phosphor material based on CaWO₄: Tb³⁺, which achieves ultra-low doping concentration temperature measurement by co-doping Li⁺ as a charge compensator. A series of CaWO₄: Tb³⁺ phosphors were synthesized using the high-temperature solid-phase method, and their structures and luminescent properties were studied. XRD Rietveld refinement shows that the introduction of Li⁺ leads to a slight reduction in lattice volume, effectively alleviating the lattice distortion caused by Tb³⁺ doping. The photoluminescence spectra show that the introduction of Li⁺ significantly enhances the luminescence intensity of Tb³⁺, as Li⁺ reduces lattice defects and improves luminous efficiency. More importantly, by optimizing the doping concentration, CaWO₄: 0.0005Tb³⁺, 0.0005Li⁺ phosphor was successfully prepared, and high-sensitivity temperature measurement was achieved. The phosphors exhibits excellent fluorescence intensity ratio and chromaticity variation in the temperature range of 293–473 K, with absolute and relative sensitivity reaching 0.21 K⁻¹ at 473 K and 2.2 % K⁻¹ at 473 K, respectively, making it an ideal material for ultra-low doping concentration optical temperature measurement.