The temperature sensing properties of Dy³⁺ and Mn⁴⁺ co-doped Ca₂LaSbO₆ phosphor

With the rapid development of modern science and technology, non-contact optical thermometry has attracted much attention in various fields. However, conventional temperature sensing methods based on the fluorescence intensity ratio (FIR) usually rely on two thermally coupled energy levels (TCELs), which inherently restrict the further improvement of temperature sensing sensitivity. Herein, a Dy³⁺ and Mn⁴⁺ co-doped Ca₂LaSbO₆ phosphor was designed and prepared to achieve high-sensitivity temperature sensing. Under 450 nm excitation, both the characteristic emissions of Dy³⁺ and Mn⁴⁺ were clearly observed. As the temperature varies, Dy³⁺ and Mn⁴⁺ exhibit different temperature-dependent luminescence characteristics. Consequently, the fluorescence intensity ratio (FIR) for temperature sensing, based on the luminescence of Mn⁴⁺ and Dy³⁺, achieves excellent performance with a maximum relative sensitivity (S_R) of 1.99% K^-1 at 425 K and an optimal temperature resolution δT of 0.23 K at 420 K. A reasonable explanation is provided for the strong thermal quenching of Mn⁴⁺ emission. The temperature-dependent fluorescence decay curves further demonstrate the existence of an additional non-radiative de-excitation pathway for Mn⁴⁺. All these results indicate that the Ca₂LaSbO₆:Dy³⁺/Mn⁴⁺ phosphor is a promising candidate material for high-sensitivity temperature sensors.