Electron microscopy study of interfacial structure and reaction of YBa2Cu3O7/Y-ZrO2 films on LaAlO3 substrates

The detailed structure and interfacial reaction of epitaxial YBa2CU3O7/Y-ZrO2 (YBCO/YSZ) films grown by chemical vapor deposition (CVD) on LaAlO3 (LAO) substrates are investigated by means of high-resolution electron microscopy (HREM), analytical transmission electron microscopy, and scanning transmission electron microscopy (STEM). The epitaxial relations of YBCO/YSZ/LAO are [100](YBCO)//[110](YSZ)//[100](LAO) and (001)(YBCO)//(001)(YSZ) //(001)(LAO). The optimum atomic configuration at the YSZ/LAO interface, in which oxygen is the first atomic layer on LAG, is proposed by using HREM combined with image simulation based on the atomic structure models of the interface. Near the YBCO/YSZ interface, two localized interfacial reaction products are formed: (i) a Y-rich modulated ZrO2 structure at the surface of the YSZ film, which may be caused by the diffusion of Y into the YSZ grains; (ii) an intergranular BaZrO3 phase formed by the diffusion of Ba along the columnar grain boundaries of the YSZ film during YBCO growth.