Accession Number : AD0656087

Title :   IONIC THERMOCURRENTS IN ALKALI HALIDE CRYSTALS CONTAINING SUBSTITUTIONAL BERYLLIUM IONS.

Descriptive Note : Technical rept.,

Corporate Author : PENNSYLVANIA UNIV PHILADELPHIA DEPT OF PHYSIOLOGY

Personal Author(s) : Bucci,Cesare

Report Date : JUL 1967

Pagination or Media Count : 30

Abstract : The dielectric relaxations of NaCl and KCl single crystals containing beryllium ions were studied by using the technique of the ionic thermocurrents (ITC) in the range of temperatures between 1.2K and 300K. The ITC spectra are characterized by three types of relaxations in both host crystals. The analysis of such relaxations and the observed temperature dependence of their relaxation times indicate that: (1) the beryllium ions are, for a large fraction, associated with cation vacancies that occupy nearest neighbor (n.n) positions as well as next nearest neighbor (n.n.n) positions with respect to the impurity; (2) the relaxation rates with which the Be-vacancy dipoles change their orientation under the influence of an electric field are dominated by the frequency of direct interchange between Be and vacancy (omega-2) and by the frequency of jump between (n.n.) and (n.n.n.) positions (omega-3 and omega-4); (3) the activation energy for the diffusion of Be ions is .5 eV for NaCl and .45 eV for KCl. In discussing the results, the possibility that the Be ions occupy off-center positions is considered. (Author)

Descriptors :   (*CRYSTAL DEFECTS, BERYLLIUM), (*ALKALI METAL COMPOUNDS, TRANSPORT PROPERTIES), (*BERYLLIUM, TRANSPORT PROPERTIES), HALIDES, IMPURITIES, DIELECTRIC PROPERTIES, IONIC CURRENT, RELAXATION TIME, DIFFUSION, HEAT OF ACTIVATION, DIPOLE MOMENTS, SODIUM CHLORIDE, POTASSIUM COMPOUNDS, CHLORIDES

Subject Categories : Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE