Transmission electron microscopic studies on crystallization of YBa2Cu3O7−y films deposited by advanced TFA-MOD method

We have prepared Y123 quenched and fully crystallized films by the conventional and the advanced TFA-MOD processes. Then, we have investigated microstructures of the films by means of transmission electron microscopy, in order to understand the initial stage of the Y123 growth. As a result, it is found that Y-Ba-O-F grains firstly nucleate on LaAlO3 single crystals as well as on CeO2 buffered metal substrates both in the TFA-MOD processes. The Y-Ba-O-F is grown with epitaxially orientated relationship to the substrate. A BaCeO3 reaction product layer is formed due to Ba diffusion from Y123 to CeO2 mainly through the grain boundaries. At the crystallization temperature of 760 °C, the diffusion rate of Ba is slow. Therefore, it was found that the thickness of the BaCeO3 layer does not increase much further with increasing the holding time until about 1000 min.