Thermal sublimation of atomically homogeneous ZnxCd1−xS powders from a single source results in films that are nonuniform in a direction normal to the substrate. This is attributed to initial preferential sublimation of Cd from the charge and is verified by energy dispersive x‐ray analyses of film cross sections and of the charge residue. These results are related to the utility of this technique for forming ZnxCd1−xS films for photovoltaic applications.