Double-site emission of Eu2+ ions in Sr4Al14O25: Eu2+ phosphors for self-calibrated optical thermometry

Eu2+ activated aluminate Sr4Al14O25 with dual-emitting centers were prepared via a solid-state method in a reductive atmosphere. Photoluminescence emission (PL) and excitation (PLE) spectra of phosphor along with the lifetimes were characterized, which confirm the 5d -> 4f energy transition behavior of Eu2+ between 400 nm and 490 nm emission. The fluorescence intensity ratio of I-490 and I-400 in the phosphors exhibits remarkable temperature dependence, owing to the diverse thermal quenching behaviors of Eu2+ emission centers. Using the phosphors to perform thermometry, excellent temperature sensitivity is achieved in the temperature range of 293-423 K. The maximum absolute and relative sensitivity are 0.004 K-1 and 0.624% at 373 K, respectively. In particular, the dual-site luminescence of Eu2+ ions can be used as the reference signal and the temperature signal of the fluorescence temperature sensor respectively. It will be helpful to develop a new self-reference optical temperature measurement technology with excellent performance.