Study of effect of quenching and deformation on KCl: Gd³⁺ crystals by using conductivity measurements

Abstract

The study of ionic conductivity vs reciprocal temperature of pure KCl and KCl crystal doped with 0.1, 0.3 and 0.5 mole % gadolinium has been carried out in as grown, quenched from elevated temperatures (100, 350 and 500°C) and annealed at various timings i.e. 2–3 h and deformed by different percentages. The plots exhibit three well-known regions, II, III and IV (extrinsic regions). The intrinsic region I was not observed in the plots as the conductivity measurements were taken up to 575°C. From the analysis of these plots, activation energies for the migration of cation vacancy and the association of gadolinium ion with cation vacancy in the lattice of KCl crystals are calculated. These values are compared with previously reported values. Further, an attempt is made to explain the existence of oxidation state of gadolinium ion in + 3 state rather than in + 2 state as reported earlier. The variation in conductivity with effect of concentration of impurity ion, quenching and annealing and deformation with various percentages are explained on the basis of formation of impurity vacancy dipoles, vacancy — vacancy pairs (which appear in the form of precipitation), storage of cation vacancies in the form of defects, introduction of fresh dislocations, etc.