CeO₂ buffer layers for HTSC via an aqueous sol-gel method : chemistry and microstructure

During the last decade the focus in superconductivity research has shifted towards the manufacturing of easy-to-handle superconductors, because of their high usability in electronic applications in comparison to bulky ceramics. This article reviews our recent progress made in the buffer layer architecture of such a coated conductor, focusing on CeO2 thin films prepared by an aqueous sol-gel method and deposited via dip-coating. Starting from water-soluble cerium(III)nitrate precursors, we were able to deposit films showing a very high degree of [002] orientation depending on the film characteristics and synthesis conditions. The formation and stability of the chemical complexes in the solution was studied via potentiometric titrations. The main influencing parameters on attaining the desired texture seem to be the ambient Ar-(5%)H2 atmosphere and the thickness of the synthesized buffer layers. The microstructure of the thin films deposited on metallic tapes was controlled via the incorporation of doping elements. This research allowed us to achieve a 50nm thick CeO2 film, showing a very high degree of [002] orientation and exhibiting a low surface roughness. Our easy-to-use, environmentally friendly strategy could contribute in the spreading of coated conductors towards everyday applications