Electron Paramagnetic Resonance Study of Radiation-Induced Defects in Ba3(PO4)2

We report an electron paramagnetic resonance (EPR) study of radiation-induced defects in Ba3(PO4)2, aiming to understand their role in radio-photoluminescence (RPL). Ba3(PO4)2 is a promising host for rare-earth dopants in optical and dosimetric applications. We compare the effects of ultraviolet (UV) and X-ray irradiation on the electron trapping by Eu3+, as well as the formation of intrinsic defects by radiation in Eu-doped and undoped samples. Both irradiation types generate Eu2+ centers with axial symmetry at one specific Ba lattice site, as confirmed by Q-band EPR. Additional EPR signals near g≈2 reveal radiation-induced centers unrelated to Eu dopants. Detailed analysis of X- and Q-band spectra identifies an H0 center and two electron-trapping defects, one tentatively assigned to an oxygen vacancy (F-type center). These findings pave the way for understanding the complex defect landscape governing charge trapping and stability in Ba3(PO4)2.