OPTIMAL PEROVSKITE-TYPE SUBSTRATES FOR HIGH-TEMPERATURE SUPERCONDUCTOR LAYERS

The lattice mismatch and stereographic maps of the prevailing epitaxial relationships for HTS on perovskite-type substrates have been determined as a function of substrate orientation. The compositions and orientations of substrates for creating perfect single crystalline HTS layers are presented. The misfit may be decreased to nearly 0 for LnGaO(3) and SrLnGaO(4), where Ln is a rare-earth ion having a large ionic radius, by optimal choice of substrate orientation. For the LnAlO(3) and (Ca, Sr)LnAlO(4) families, good lattice match is lacking. The best compounds among them are LaAlO3 and SrLaAlO4. Because of the weak orientation dependence of the misfit for SrTiO3 and the LnAlO(3) family, the main purpose of substrate orientation optimization is to suppress polysynthetic twinning.