With the decrease in the size of cubic silver halide crystallites, the resolution of
silver halide photographic emulsion increases, meanwhile, its sensitivity decreases rapidly.
The structure of silver halide microcystal grains has great influence on the sensitivity. In this
paper, the design principle of multi-structure silver bromo-iodide is investigated. Silver halide
photographic emulsion with multi-structure grains is precipitated by auto-controlled double jet
machine. TEMand XRD analyses showthat iodide-rich layer is composed ofAgBr0.831I0.17, in
which iodide is not distributed uniformly and mainly located near the corners of the cubic core
grains. XPS analysis shows that the surface of multi-structure grains contains some iodide ions
though no iodide has been added, suggestingthatthe iodide ions have the tendencyof diffusing
outwards. In addition, the experimental phenomena are explained in theory.