Vacancy formation parameters from isoelectric temperatures in calcium-doped potassium chloride

Abstract

Abstract Using the ultrasonic piezoelectric composite oscillator technique, the temperature dependence of dislocation charge in bent KCI single crystals has been measured as a function of Ca impurity concentration. In each case the charge changes sign at an extrinsic isoelectric temperature, T e. The shift in T e with impurity concentration allows the individual thermodynamic vacancy formation parameters, h +, S +, h − and S −, to be measured. Assuming the temperature-independent Schottky parameters of Chandra and Rolfe (1970), we obtain h + = 1·256±0·008eV, S +=453±0·10k, h − = 1·334∓0.008eV and S − = 5·08∓0·10k. The possible temperature dependence in these parameters is investigated.