THERMOLUMINESCENCE SPECTRA OF DOPED BI4GE3O12

Thermoluminescence of Bi4Ge3O12 reveals a range of trapping levels whi ch are common to pure and doped material. The relative intensities of the glow peaks observed above room temperature change with radiation d ose and dose rate and the presence of impurities. Although the trappin g sites are thought to be intrinsic oxygen defects, additions of impur ities enhance the signals from different glow peaks. The emission spec tra from pure and transition ion doped Bi4Ge3O12 extend from 450 to 75 0 nm. If rare earth ions are present then they act as the dominant rec ombination centres and define the emission spectra. This is interprete d as resulting from direct charge transfer from intrinsic defect traps to rare earth recombination centres. The close interaction of trap an d rare earth is evident by a temperature dependence of the 110 and 175 degrees C glow peaks with the ionic radii of the impurities. Models f or the charge traps are proposed and activation energies are given.