Role of dopant on the formation of SO3- radical induced by X-ray irradiation in K3Na(SO4)2 crystals

The electron spin resonance (ESR) and thermoluminescence (TL) spectra were measured in the K3Na(SO4)2 sample doped with rare earth (Ln: Y and lanthanoid), Al or In ion after X-ray irradiation. The paramagnetic radicals (SO3- and SO4-) were produced by the irradiation of X-ray in the Ln, Al or In ion-doped sample. The ESR signal intensity due to SO3- radical was very high in doping with stably trivalent Y, La, Gd or Lu ion, especially doping with Y or Gd ion of size similar to that of Na ion, while it was low in the Al or In ion-doped sample. In addition, it was remarkably low in the Sm or Eu ion-doped sample. The TL spectra were observed to examine the valence of rare earth ion doped in the K3Na(SO4)2 matrix. The TL spectrum was ascribed to the f-f transition of Ln3+ in the Pr, Nd, Gd or Tm ion-doped sample. The TL spectrum was also ascribed to the f-f transition of Sm3+ and the f-d transition of Sm2+ in the Sm ion-doped sample and the f-d transition of Eu2+ in the Eu ion-doped sample. These results suggest that their dopant is predominately substituted for Na ion in the K3Na(SO4)2 matrix, and the formation of SO3- radical is promoted by the cation vacancy which was produced by the charge compensation due to doping of trivalent ion. (Copyright (c)1999 Elsevier Science B.V., Amsterdam. All rights reserved.)