Analysis of space charge relaxation by equivalent electric circuit for yttrium doped CaF2

Characteristic behaviours of high temperature ionic thermocurrent (HT ITC) in CaF2:Y were studied by a usual ITC method with Teflon insulated electrod es in the nominal yttrium concentration range from n = 0.002 to 30 mol%. An equivalent electric circuit was used to analyze HT ITC by assuming a space charge how model with a specific resistivity in the form of rho(T) = rho(s ysc) T exp(E-a/kT). The analysis revealed that a relaxation of the space ch arges occurred in the specific resistivity from insulating to semi-insulati ng change-over of CaF2:Y crystal. In addition, dependences of the peak temp erature shift and total charge of HT ITC on the crystal thickness could be explained by taking into account the capacitance of the crystal. And the yt trium concentration dependence of the activation energy for the space charg e flow could be well approximated by E-a(n) = E-ao = gamma n(1/3). (C) 1998 Elsevier Science Ltd. All rights reserved.