The mechanism of the nano-CeO2 films deposition by electrochemistry method as coated conductor buffer layers

•Crack-free CeO2 film thicker than 200 nm was prepared on NiW substrate by ED method.•Different electrochemical processes as hydroxide/metal mechanisms were identified.•The CeO2 precursor films deposited by ED method were in nano-scales.

Comparing with conventional physical vapor deposition methods, electrochemistry deposition technique shows a crack suppression effect by which the thickness of CeO2 films on Ni–5 at.%W substrate can reach a high value up to 200 nm without any cracks, make it a potential single buffer layer for coated conductor. In the present work, the processes of CeO2 film deposited by electrochemistry method are detailed investigated. A hydroxide reactive mechanism and an oxide reactive mechanism are distinguished for dimethyl sulfoxide and aqueous solution, respectively. Before heat treatment to achieve the required bi-axial texture performance of buffer layers, the precursor CeO2 films are identified in nanometer scales. The crack suppression for electrochemistry deposited CeO2 films is believed to be attributed to the nano-effects of the precursors.