Gamma-ray-induced enhancement of red emission in Ga2-xEuxO3 phosphors for harsh radiative environment applications

Eu³⁺-doped β-Ga₂O₃ (Ga_2-xEu_xO_3, x = 0.01–0.06, Δx = 0.01) red phosphors were fabricated in cylindrical pellet shape via the solid-state reaction route. An in-depth analysis of photoluminescence (PL), surface morphology, three-dimensional profiles, crystal structure, and X-ray photoelectron spectroscopy spectra has been carried out both before and following exposure to a 2 Mrad dose of gamma-ray irradiation. The PL results revealed that gamma-ray-irradiated samples have significantly higher luminescence intensity compared to their counterparts. Notably, for the sample with a 5 % Eu³⁺ doping concentration, the luminescence intensity of the red emission, which peaks at 613 nm under 394 nm excitation, increased by 14.5 ± 1 % after irradiation. This phenomenon challenges the conventional wisdom that high-energy radiation always degrades optical properties. We demonstrate that gamma rays create beneficial defects (e.g. oxygen vacancies and lattice distortions) that suppress non-radiative recombination and enhance Eu³⁺ emission. Additionally, the Ga_2-xEu_xO₃ samples demonstrated remarkable durability to gamma-ray radiation up to a dose of 2 Mrad, which corresponds to the cumulative radiation dose experienced by satellites in low-Earth orbit over nearly 80 years. These optical and structural properties suggest that the Eu³⁺-doped Ga₂O₃ is a promising red phosphorescent material for applications in harsh radiative environments.