Electronic Trap Defects in Y2O3:Eu and (Y,Gd)2O3:Eu X-Ray Scintillators

Abstract

ABSTRACTDetailed properties of the defects and energy transfers responsible for afterglow in transparent sintered ceramic Y2O3:Eu and (Y,Gd)2O3:Eu based scintillators have been determined by transient thermoluminescence ('TL) and spectral measurements of afterglow emission. X-ray excited TTL spectra between 150 K and 350 K reveal 4 defect transitions for 3 mole percent Eu. Adequate modeling of this data requires for each defect transition a trap depth energy, an attempt-to-escape frequency, a broadened density of trap state energies, and a trap filling frequency. These defect parameters have been determined and can be used to predict afterglow dependence on time after excitation shut-off, exposure time, and temperature. The afterglow emission spectra at all temperatures are characteristic of Eu under S6 site-selective UV excitation of these rare-earth C-type structure scintillators. This indicates that states associated with the Eu activator on the S6 site are the terminal states upon thermal release of trapped charge carriers.