The growth of REBa2Cu3O7-δ (REBCOZrare earth elements) high-temperature superconducting thick films by liquid phase epitaxy is reviewed, which are most promising for electronic device and coated conductor applications. The paper focused on thermodynamic relations, chemical reactions and physical phenomena in the liquid phase epitaxy process, which are closely related to the control of the microstructures and properties of materials. Recent progresses achieved and the problems to be solved have been reviewed in above sections.

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

In the air atmosphere, high superconducting transition temperature (Tc) Nd1+χBa2-χCu3O7-δ (NdBCO) single crystals were grown by top-seeded solution-growth (TSSG) Two controllable thermodynamical parameters, i.e. liquid composition and growth temperature were focused on. Using the ratio of Ba to Cu (Ba:Cu) at 0.78 in the liquid, the grown NdBCO crystal displays onset Tc of 94.6K with a sharp transition width DT less than 1.5K. The Ba-rich liquid leads to the lower substitution of Ba with Nd in grown crystals, resulting in the higher Tc. This finding suggests that the Ba: Cu ratio in the liquid is a very important processing parameter for obtaining higher Tc of the NdBCO uperconductors. In addition, the higher Tc as well as the lower Nd substitution can be achieved when using the lower growth temperature. These results are consistently interpreted by the NdO1.5-BaO-CuO ternary phase diagram.

Using YBCO/MgO thin films, for the first time, we report a success in the melt-textured growth of YBCO bulks by the cold-seeding method. The grown bulk has a good orientation relation of YBCO 〈100〉 bulk Ⅱ YBCO 〈100〉 film Ⅱ MgO 〈100〉 substrate. In this process, the YBCO film withstood heating over its peritectic temperature (up to 1045℃) for 1.5 h and acted as a seed for the YBCO bulk growth, indicating an intrinsic superheating property, which was reported in other work. The unique superheating mechanism in this study was clarified. It was found that the a-b alignment of YBCO film plays a key role in controlling the single grain growth of YBCO bulk.

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.