Dependence of Tl response of CaSOsub(4):Dy and CaSOsub(4):Tm on grain size

CaSOsub(4):Dy and CaSOsub(4):Tm were prepared by crystallization from hot sulfuric acid containing a small amount of hydrogen peroxide. The addition of hydrogen peroxide influences the grain size of the crystals produced. In the case of CaSOsub(4):Dy and CaSOsub(4):Tm phosphors the dependence of TL sensitivity upon grain size, especially that ranging higher than 63 μm was examined. The fraction of grain diameter 63-200 μm was found to be the most sensitive and with increasing grain size the sensitivity decreased. For two samples the decrease of TL sensitivity was similar to that of the activator concentration determined by the XRF method, while in the case of the other two samples no significant change in the activator concentration with the grain size could be stated. Accordingly, the TL response is influenced by several other factors as well. On the glow curve, the TL peak at a temperature of about 110 deg C decreased with the increase of grain size. (author)