A glass phosphor is an attractive material for applications in radiation detection because of its high workability and availability with a wide range of chemical compositions. Recently, the X-ray-induced luminescence of glasses containing various luminescent activators has been actively investigated worldwide. Among them, glass that exhibits the radio-photoluminescence (RPL) phenomenon is a promising material for not only dosimetry but also X-ray imaging applications. However, there are only a few materials that exhibit the RPL phenomenon, and thus there is room for material exploration. In this study, we found that Ag2O–R2O–BaO–Al2O3–P2O5 (R = K, Rb, Cs) glass, in which some of the constituents of the commercial RPL glass were replaced with heavy elements, shows RPL properties worthy of practical application. Our glass specimens have a spatial resolution of at least 8 LP/mm; furthermore, the fading of the emission from RPL centers was much lesser than that from commercial imaging plates.