Abstract: The preparation of shell layer of multi-structure silver bromoiodide cubic microcrystals was studied. During the preparation of shell layer, the pAg value TAI and ammonia affected crystal growth and renucleation apparently. For AgBr cubes, the number of renucleated crystals was increased with the increase of pAg value or the adding of TAI under the same reactant addition rate. The crystal habit was transferred from cube to octahedra when TAI existed. The number of renucleated crystals was decreased when ammonia existed.The sensitivity wasn’t increased apparently when adding rate ratio of the reactant reached 13.3 under the condition of our experiments. But it was affected by silver quantity ratio between seed and shell. Sensitivity was increased about 80% when the silver quantity ratio between seed and shell was increased from 0.831 to 4.51, at the same time fog was almost unchanged.

Key words: silver bromoiodide, multi-structure, shell layer