Protective oxide coatings for superconducting YBa2Cu3O7-x thin films

The feasibility of yttria stabilized zirconia (YSZ) and CeO2 films as protective coatings for YBa2Cu3O7-x(YBCO) has been tested. Protective YSZ and CeO2 films have been deposited by laser ablation on high quality epitaxial superconducting YBCO thin films under various oxygen partial pressures and temperatures between room temperature and 200 C. Dense and well adhered coatings can be obtained at low pressures around 10-4 mbar even at room temperature. Polycrystalline CeO2 films with (hhh) and (00h) orientations are obtained even at room temperature. At 200 C, (00h) epitaxial growth with <110>CeO2 direction parallel to a/b axes of YBCO is observed. The deposition of CeO2 films has no detrimental effect on the electrical properties of YBCO films, whereas a reduction in the critical temperature is observed when YBCO is coated with YSZ at 200 C at low pressures. Coated YBCO films keep their electrical properties unchanged when they are exposed to extreme humidity conditions for which bare films are completely destroyed. (orig.)