Interplay of Optical Traps and Vibronic Thermalization Governing Mn ²⁺ Luminescence in Ca ₁₉ Ce(PO ₄ ) ₁₄ : Implications for Temperature Sensing and Thermal Threshold Indicator

The development of advanced luminescent thermometric materials requires the identification of novel mechanisms capable of inducing temperature‐dependent changes in the spectroscopic properties of phosphors. In response to this need, the present work demonstrates a cooperative effect involving the thermalization of the 4 T 1 ( 4 G) ‐level components of Mn 2+ ions and trap → 4 T 1 ( 4 G) energy transfer in Ca 19 Ce(PO 4 ) 14 :Mn 2+ . This interplay results in a simultaneous enhancement of the 4 T 1 ( 4 G) → 6 A 1 ( 6 S) emission band intensity accompanied by a blue shift of its spectral position with increasing temperature. This phenomenon can be effectively utilized for temperature sensing and imaging applications. Furthermore, the distinct thermal responses of Ce 3+ and Mn 2+ luminescence enable not only the determination of the luminescence intensity ratio ( S R = 4.5% K −1 ), but also the development of a luminescent indicator for detecting the crossing of a threshold temperature using the RGB channels of a standard camera. Importantly, the activation temperature of the signal in the G channel, which is governed by the Mn 2+ ion concentration, provides a means to tune the threshold temperature of the sensor. This allows for precise adjustment of the sensor performance to meet specific application requirements.