The Strain-ageing of Silver Halides

Presented, in part, at the 42nd Annual Conference of SPSE, Boston. U.S.A., May 15–19. 1989.

Abstract

A study has been made of straillageing in silver llalide single crystals. At room temperature the behaviour of wIle-refined material is dominated by a hardening that is allributed to the pinning of slip-dislocations by impurities: the hardening shows a time-dependence that follows the Cottrell-Bilby law. the rate of hardenillg increases with increase in temperature over moderate ranges, the activation energy of the hardening process is 0.40±0.01 eV and the addition of cadmium in the range 0-200 p.p.m. produces an increase in the hardening rate with an activation ellergy of 0.42 ± 0.03 eV.

At temperatures above about 400 K the zonerefined material shows two-stage recovery and 110 hardening. The first stage appears to be COIl trolled by the divalellt impurity content of /lIe material while in the second stage the rate controllingprocess is probably the diffusion of chloride ion vacancies from jogs in screw dislocations.

At 77 K the zone-refined material also shows two-stage recovery, the first of whicll is thought to be due to minor rearrangements of dislocations within slip barlds. while the second is probably controlled by the cross-slip of screw dis location around jogs.

Highly pure silver bromide shows no hardening on ageing. whatever the temperature, while the addition of iodide at ≈,1 mol % into the zonerefirled material produces a further hardening process.

Notes

Presented, in part, at the 42nd Annual Conference of SPSE, Boston. U.S.A., May 15–19. 1989.