Role of dopant on the formation of SO 3− radical induced by X-ray irradiation in K 3Na(SO 4) 2 crystals

Abstract

The electron spin resonance (ESR) and thermoluminescence (TL) spectra were measured in the K 3Na(SO 4) 2 sample doped with rare earth (Ln: Y and lanthanoid), Al or In ion after X-ray irradiation. The paramagnetic radicals (SO 3 − and SO 4 −) were produced by the irradiation of X-ray in the Ln, Al or In ion-doped sample. The ESR signal intensity due to SO 3 − 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 K 3Na(SO 4) 2 matrix. The TL spectrum was ascribed to the f–f transition of Ln 3+ in the Pr, Nd, Gd or Tm ion-doped sample. The TL spectrum was also ascribed to the f–f transition of Sm 3+ and the f–d transition of Sm 2+ in the Sm ion-doped sample and the f–d transition of Eu 2+ in the Eu ion-doped sample. These results suggest that their dopant is predominately substituted for Na ion in the K 3Na(SO 4) 2 matrix, and the formation of SO 3 − radical is promoted by the cation vacancy which was produced by the charge compensation due to doping of trivalent ion.