We present a detailed investigation of thechemistry at the growth interface between the bottomelectrode and ferroelectric film in (001)-oriented epitaxialferroelectric thin-film heterostructures. Three differentferroelectric systems, namely PbZr0.2Ti0.8O3, PbZr0.52Ti0.48O3, and BaTiO3 deposited on SrRuO3/SrTiO3, wereinvestigated to compare and contrast the role of latticemismatch versus the volatility of the deposited cationspecies. A combination of transmission electron microscopy-based imaging and spectroscopy reveals distinctcorrelations among the ferroelectric thin-film composition,the deposition process, and chemical gradients observedacross the ferroelectric–electrode interface. Sr diffusionfrom the electrode into the ferroelectric film was found tobe dominant in PbZr0.2Ti0.8O3/SrRuO3/SrTiO3 thin films.Conversely, Pb diffusion was found to be prevalent inPbZr0.52Ti0.48O3/SrRuO3/SrTiO3 thin films. The BaTiO3/SrRuO3/SrTiO3 heterostructure was found to have atomicallysharp interfaces with no signature of any interdiffusion.We show that controlling the volatility of the cationspecies is as crucial as lattice mismatch in the fabricationof defect-free ferroelectric thin-film devices.