Seamless triple-mode luminescence thermometry in Lu3(Al4Ga1)O12:Pr: high sensitivity from 11 to 700 K

This study reports on the high-performance luminescence thermometry of a Lu 3 (Al 4 Ga 1 )O 12 :Pr (LuAGG:Pr) phosphor, demonstrating a remarkable operational range spanning from deep-cryogenic to high-temperature regimes (11–700 K). Its relative thermal sensitivity, S r , remains between 0.7% and 6.5% K −1 , exceeding 1% K −1 over the vast majority of this interval. To overcome the sensitivity bottlenecks inherent to single-parameter thermometers, we propose a multi-mode thermometric strategy that leverages three distinct physical mechanisms. At cryogenic temperatures (11–120 K), the population redistribution among the Stark levels of the 1 D 2 state yields a maximum S r of 6.5% K −1 . In the intermediate range (120–320 K), sensing is governed by the Boltzmann-coupled 3 P 1 and 3 P 0 states, yielding a maximum S r of 5.5% K −1 when using the two-level emission ratio. Crucially, we demonstrate that the integration of the intensity ratio between the interconfigurational 5d→4f and 1 D 2 → 3 H 4 emissions - primarily driven by multiphonon relaxation - significantly enhances performance at elevated temperatures. While Boltzmann-type distributions show declining sensitivity above room temperature, this multiphonon-driven 5d/4f ratio revitalizes the sensor, maintaining S r > 1% K −1 up to 700 K, with S r peak of 2.2% K −1 at 465 K. By strategically combining these three parameters, we achieve a continuous, high-sensitivity profile across the entire 11–700 K window, establishing LuAGG:Pr as one of the most versatile Pr 3+ singly activated materials for advanced thermal sensing reported to date.