The temperature dependence of dislocation charge in calcium doped single crystals of potassium chloride

Abstract

Using the ultrasonic piezoelectric composite oscillator technique we have measured the temperature dependence of dislocation charge in bent KCl single crystals as a function of Ca impurity concentration. In each case the charge changes sign at an extrinsic isoelectric temperature, T_e , and the shift in Te with impurity concentration allows the calculation of the individual thermodynamic vacancy formation parameters. We obtain h₊ = 1.244±0.014 eV, s₊ = 4.50±0.19 k, h- = 1.346∓ 0.014 eV and s- = 5.11∓0.19K.