Abstract: The monodispersive octchedral AgBr (0.8 μm) emulsion was prepared by the double-jet method. After doping I~- (1×10~(-3)-4×10~(-2)mol I~-/mol AgBr) on the sur- face of AgBr, the dielectric absorption peak of samples shifted gradually to hi- gher frequencies. When doped I~- content is lower than 1×10~(-2)mol/mol AgBr, the absorption peaks are dispersive. When doped I~- content is≥1×10~-mol/mol AgBr, the absorption peaks are sharper and do not shift markedly to higher frequencies any longer. In the sample with 1×10~(-2) mol I~-/mol AgBr, the strongest X-ray diffraction peak (002) of AgI has been observed. In the sample with 4×10~(-2) moo I~-/mol AgBr, three strongest peaks (100), (002), (110) of the β-AgI have been obsrved. The results of X-ray analysis show that these AgI are chiefly epitaxial on the surface of AgBr by substitution. On the average, 1 mol% I~- can substitute about five layers Br~- ions on (111) surface of AgBr (0.8 μm).
From the above experimental results, it may be considered that the thickness of the surface layer which influence on the interfacial polarization is about 0.2 nm. In this thickness range, if I~- distribution is heterogeneous, the dielectric absorption peak of sample will be getting dispersive.