Eu3+ as Optical Probe for Perovskite Phase Transition: A Case of LaGaO3:Eu3

ABO3 perovskite can accommodate different luminescent activators, e.g., lanthanoid ions at the A site and transition metal ions at the B site, resulting in diverse perovskite phosphors with attractive luminescent properties. Herein, spectroscopic measurements under high-temperature and high-pressure conditions were conducted to investigate the phase transition behavior of perovskite-type LaGaO3 using Eu3+ as a luminescent probe. The 5D0 → 7F2 electric dipole (ED) transition of Eu3+ is sensitive to local structural symmetry, while the 5D0 → 7F1 magnetic dipole (MD) transition is relatively insensitive. Changes in the luminescence intensity ratio (LIR) of 5D0 → 7F2 (610-630 nm) to 5D0 → 7F1 (590-600 nm) induced by heating and compression were analyzed. Significant variations in the Stark splitting of the 7FJ (J = 1, 2) levels and the LIR were observed in specific temperature ranges, indicating phase transitions can be precisely detected through an optical approach using Eu3+ transitions. Furthermore, the pressure-induced phase transition behavior of LaGaO3 was successfully observed, and comparatively high relative pressure sensitivity (Sr(p)) of 41.7%GPa-1 was obtained at 2.62 GPa and 31.0%GPa-1 at 3.54 GPa, respectively. These results provide insight into optical detection of structural phase transitions using Eu3+-activated perovskites.