High Tc Y-Ba-Cu-O Superconducting Thick Films Fabrication and Film/Substrate Interactions
High Tc Y-Ba-Cu-O superconducting thick films having Tc at 87 K and R=O at 79 K have been successfully made by using conventional thick film screen printing technology on MgO and ZrO2 substrates. Film/substrate interactions were examined by electron microprobe analysis as a function of starting powders, heat treatments and substrates. At processing temperatures of 950°C, Ba and Y enrich at the substrate reaction boundary layer (~ 2 μm thick) with depletion of Cu in the superconductor for all the substrates we examined. On the other hand, Cu segregates more at the interface layer than Y and Ba in films fired at 900°C. The fired film microstructures were found to vary strongly with starting powders which demonstrated quite a difference in both densification and grain growth rates. Good superconducting films were never achieved on an alumina substrate. Limited film/substrate interactions were proved to preserve superconducting integrity and to have adhesion greater than 20 newtons, which is adequate for most of microelectronic applications.
KeywordsThick Film Alumina Substrate Superconducting Phase Precursor Powder Reaction Boundary Layer
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