Ultrasonic Composite Oscillator Research Articles

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

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.

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, Te , 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.