Electro- and photon-induced cooling in BNT-BT-SBET relaxors with in situ optical temperature sensing

Abstract

A novel lead-free luminescent ferroelectric (FE) ceramic, B i 0.5 N a 0.5 T i O 3 − 0. 06 B a T i O 3 − 0. 055 S r 0.7 B i 0.18 E r 0.02 ◻ 0.1 T i O 3 (BNT-BT-SBET), is developed with an adiabatic temperature change ( Δ T ) of 0.7 K under an electric field ( E ) of 60 kV/cm at room temperature, an anti-Stokes fluorescence cooling, and a maximum optical T sensitivity of 0.0055 K − 1 at 522 K. Interestingly, the electrocaloric response reaches a saturation at permittivity shoulder T of 100°C; meanwhile, the maximized emission intensity of 2 H 11 / 2 → 4 I 15 / 2 occurs. T - and E -tunable enhancement of 2 H 11 / 2 → 4 I 15 / 2 emission intensity is due to the population inversion from the 4 S 3 / 2 to 2 H 11 / 2 states caused by an incoherent regime consisting of FE phase and polar nanoregions in a relaxor matrix.