EFFECT OF PR-CODOPING ON THE X-RAY-INDUCED AFTERGLOW OF (Y,GD)(2)O-3-EU

The afterglow properties of (Y,Gd)(2)O-3:Eu ceramics and related defec ts formed by X-ray irradiation have been investigated. Temperature-dep endent afterglow measurements have been compared with thermoluminescen ce curves and it has been found that afterglow of (Y,Gd)(2)O-3:Eu is c aused by thermally unstable trapped charge carriers. Codoping of Pr re sults in a strong decrease of afterglow. During X-ray irradiation Pr4 is formed, which has been identified by comparing absorption spectra of X-ray irradiated and oxidized samples. Thermoluminescence measureme nts of (Y,Gd)(2)O-3:Eu,Pr show that Pr3+ acts as an effective hole tra p which successfully competes with the intrinsic hole traps and is fou nd to be stable up to 700 K. The thermally unstable intrinsic hole tra ps which are responsible for the high afterglow at room temperature ar e no longer occupied and therefore afterglow is drastically reduced.