Anelastic and dielectric relaxation due to impurity-vacancy complexes in NaCl crystals

Appreciable pairing of divalent metallic impurities with Na+ vacancies occurs in NaCl below 300°C. The reorientation of such pairs or complexes had previously been observed under an applied electric field. In the present work stress-induced reorientation of pairs in NaCl doped with CaCl2 and MnCl2 has been studied by means of internal friction measurements. An internal friction peak attributed to pair reorientation under stress was observed near 100°C for a vibration frequency of ∼10kc/sec. Data obtained for longitudinal stress along both theata.