Accession Number : AD0608827

Title :   BREAKDOWN STRENGTH OF ALKALI HALIDES AS FUNCTION OF TEMPERATURE AND DISLOCATION DENSITY,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR INSULATION RESEARCH

Personal Author(s) : Nevald,Rolf

Report Date : OCT 1964

Pagination or Media Count : 22

Abstract : The d-c breakdown strength of NaCl, RbBr, and KI single crystals was measured from 4.2 to 400K. The characteristics consist of a slow rise at low temperatures followed by a steep decrease in the high-temperature region. The positive slopes at low temperature conform to theoretical expectation based on the von Hippel criterion of impact ionization. The position of the maxima for the different crystals corresponds approximately to the temperaturef where the ionic current densities in the various materials are identical. The electric strength of NaCl crystals was measured as function of temperature for four different dislocation densities. Low dislocation concentrations, as found in normally prepared crystals, have no noticeable effect. For high dislocation densities, the rising section of the characteristic flattens, the falling section steepens, and the maximum shifts to lower temperatures. These trends conform with previous findings on the effect of addition agents and the transition from crystal to glass. The dislocations were found to cause a dielectric relaxation spectrum in the 10 to the 3rd to 10 to the 8th power Hz region. (Author)

Descriptors :   (*SINGLE CRYSTALS, ELECTRICAL PROPERTIES), (*DIELECTRICS, DEGRADATION), (*ALKALI METAL COMPOUNDS, HALIDES), CRYSTAL DEFECTS, THERMAL PROPERTIES, SODIUM COMPOUNDS, FLUORIDES, CHLORIDES, RUBIDIUM COMPOUNDS, BROMIDES, POTASSIUM COMPOUNDS, IODIDES, IONIZATION, IONIC CURRENT

Distribution Statement : APPROVED FOR PUBLIC RELEASE