PREPARATION AND STUDY OF EPITAXIAL AGCL AGBR(I) CUBIC GRAINS

Three AgCl/AgBr(I) cubic emulsion grains were prepared successfully by epitaxial deposition of AgCl on (111) surfaces of three cubo-octahedr al AgBr(I) host grains made at various pAg values by a microcomputer-c ontrolled, balanced, double-jet method. Using powder X-ray diffractome try, the component phases of these epitaxial emulsion grains were iden tified, corresponding to the host AgBr(I) phase and a new AgCl phase, respectively. The dielectric loss curves of epitaxial grains showed tw o separated peaks, corresponding to the contribution of the AgBr(I) ho st phase and epitaxial AgCl to ionic conductivity, respectively. The p hotoconductivity decay process for both host and epitaxial grains was composed of slower and faster parts, each of which obeys first-order k inetics. The epitaxial procedure modified effectively the amount and m ean lifetime of photoelectrons. The photosensitivities of epitaxial em ulsions were much higher than those of the host emulsions, which can b e attributed to the epitaxial growth benefiting the formation of conce ntrated latent image.