Scintillation and luminescence characteristics of a highly dense transparent YAG: Ce-ceramic are reported and compared to those of a single crystal. When excited with gamma-rays both types of materials display the same dominant ≈85 ns decay, but the ceramic also shows a new rapid component of ≈20 ns that is completely absent in the single crystal. The scintillation output from the ceramic reaches about 50% of that from the single crystal, having been diminished by unusual loss processes caused by the deformed lattice at the grain boundary interfaces. A phenomenological model involving distortion of the band structure is proposed to explain the results of kinetic measurements.

The concept of optical temperature sensing using band intensity ratio is considered as one of the most effective, self‐reference, non‐invasive, and rapid detection techniques for the local temperature in natural or engineered systems. In this work, for the first time a divalent lanthanide‐co‐doped dual‐center system, i.e., SrB₄O₇:Eu²⁺/Sm²⁺ phosphors, working as a bifunctional ratiometric sensor of temperature and pressure is employed. With temperature alterations, the Eu²⁺/Sm²⁺ luminescence intensity ratio and the emission lifetime of Sm²⁺ are significantly changed, showing unprecedentedly high relative sensitivity of 45.6 and 3.17% K^‐1, respectively. Moreover, in the pressure range from ≈10 to 40 GPa, the intensity ratio of the Eu²⁺/Sm²⁺ emissions shows strong pressure dependence and can be utilized for pressure monitoring, with high pressure relative sensitivity of ≈13.8% GPa^‐1. The superior performance indicates that the developed dual‐center Eu²⁺/Sm²⁺‐co‐doped SrB₄O₇ phosphors are promising candidates for supersensitive optical sensing applications. The findings open a new approach of designing optical temperature and pressure sensors.