We report a novel-superheating phenomenon inYBa2Cu3Oz (Y123) oxide films (over 45K), whichwere prepared by vapour deposition onMgOsubstrates. The origin of this superheating could be mainly attributed to the positive change of surface energy in peritectic melting, during which Y123 melts into the Y2BaCuO5 (Y211) solid and the Ba-Cu-O liquid. It was found that the heterogeneous melting initiates at the Y123/MgO interface and the molten liquid does not wet MgO and Y123. These melting features of Y123 films explain the delaying of the melting process.

Using the top-seeded solution-growth (TSSG) method, Cu-site-substituted REBa2Cu3O7-d single crystals (REBCO, RE

In this communication, for the first time, we report on a high-Tc 95K Sm1+xBa2−xCu3Oz (SmBCO) single crystal with a small transition width of less than 0.5K grown under 1 atm oxygen pressure. We found that the substitution of Ba by Sm could be effectively suppressed by using liquid composition control. Jc-B curves and scaling analysis of samples at 77K with B Ⅱ c indicate that a delta Tc style defect is the predominant pinning in SmBCO crystals.

YBa2Cu3O7-dδ (YBCO) thin films were used as seed films for growing high peritectic temperature (TP) Nd1+χBa2-χCu3O7-δ (NdBCO) thick films by liquid phase epitaxy. On heating to a temperature above TP; polycrystalline YBCO grains agglomerate and then partially decompose. The metastable YBCO phase takes the lowest energy configuration, an enlarged size and a shape with an equilibrium curvature, which prohibits them from immediate decomposition and dissolution. As a result, the retained YBCO grains act as heteroeptaxial-seeds for the growing NdBCO grains in the Nd-Ba-Cu-O solution. Yttrium was detected in the NdBCO grains grown in the initial stage by EPMA, strongly supporting a model of the YBCO-seeded NdBCO growth.

Abrupt transition from a-axis growth to c-axis growth was found in the liquid phase epitaxy LPE process of YBa2Cu3Ox YBCO or Y123 on 110 NdGaO3 substrate. Subsequently, the influence of supersaturation and liquid composition on the orientation of LPE thick films was systematically studied. Dissimilar to the thin film deposition, the a-phase growth was predominant at a low supersaturation about 17K, especially grown by using a Cu-rich melt. The investigation of the initial stage of YBCO growth was performed, in which we found the protruding epitaxial a-axis grains and preferentially a-phase nucleation on the c-dominated thick film. The energy dispersive x-ray spectrometry attached scanning electron microscope was employed to confirm the composition of the outgrowth of long-axis grains, as well as the microstructure around the dipping boundary line in the initial growth. Based on the "nucleation and growth" mode, a comprehensive description of the competition between a-axis and c-axis growth under various growth environments was given, which further unveiled the origin of a-c transition in YBCO thick films.