Thermal‐Energy‐Boosted Luminescence for Precise Optical Thermometry in Eu/Tb‐Doped ScNbO₄

Abstract Rare‐earth‐ion‐doped luminescent materials are promising candidates for remote optical thermometry because of their temperature‐sensitive optical properties. Among various techniques, fluorescence intensity ratio (FIR) methods, particularly those based on thermally coupled levels (TCLs) in excited states, are widely used. However, challenges such as limited spectral separation and low luminescence contrast at elevated temperatures limit their performance. In this study, a novel strategy is proposed that utilizes the thermally‐coupled ground states of Eu 3+ in ScNbO 4 to enhance the FIR contrast through thermal energy assistance. This approach leads to a notable increase in the Eu 3+ luminescence intensity with increasing temperature. Additionally, Tb 3+ ‐doped ScNbO 4 is employed as a self‐calibrating reference and exhibited typical thermal quenching behavior. By combining these opposing luminescence responses, where Eu 3+ emissions increase while Tb 3+ emissions decrease, a high‐contrast optical thermometry system is developed with enhanced sensitivity and stability. This system achieves a relative sensitivity of 5.48%K −1 at 410 K, with strong spectral discrimination at 550 and 614 nm. The results demonstrate that this approach effectively integrates the advantages of both the TCL and non‐TCL mechanisms, offering a promising pathway for high‐precision optical thermometry.