Imperfections in due to the in‐diffusion of zinc at temperatures in the range of 700°–1100°C have been investigated by means of x‐ray diffraction topography, optical microscopy, and infrared transmission microscopy. The imperfections, which were generated in the diffused layer, were identified as submicroscopic precipitates. Precipitation was almost unavoidable when metallic zinc was used as the diffusant source. Although precipitation could be prevented when was used as a source, prolonged diffusion always resulted in precipitation. It was concluded that diffusion‐induced dislocations plus precipitation, or diffusion‐induced precipitation alone, was occurring in our samples.