Abstract
In this study, Campbell's solution for instantaneous source diffusion was reanalyzed. A diffusion system consisting of a homogeneous rectangular slab of thickness y 0 , containing a straight grain boundary of width 2a along the positive axis of a cartesian coordinate frame was considered. A new solution was derived that satisfies all the conditions of the diffusion system. On the other hand, Campbell's solution does not satisfy the initial condition nor the condition of conservation of the total amount of diffusant. These results indicate that the derived solution is the correct solution for grain boundary diffusion in a thin film with an instantaneous source.