High-temperature creep of single crystalline sodium chloride

Abstract

An investigation of high-temperature creep of sodium chloride has been conducted on single crystalline specimens with {001} faces, compressed along a 〈001〉 direction. It is shown that, for all compression tests in the conditions of duplex slip, the barrel-like shape obtained is not a drawback; lubrication of the compression faces is unnecessary and it is possible to maintian a constant stress by calculated load increments. The stress dependence of the steady-state creep rate can be fitted to a power law with an exponent n = 4·2. The activation energy of the creep rate has been found equal to 2·5 ev in the temperature range from 750°c to 795°c, for pure NaCl or crystals doped with 450 p.p.m. Sr⁺⁺ ions. It is proposed that high-temperature creep of NaCl is due to glide on {110} planes of predominantly edge dislocations and controlled principally by the diffusion of neutral vacancy pairs to and from neutral jogs.