REBCO厚膜的液相外延生长研究

本文从基片和种膜、LPE的初始阶段研究和超导性能的控制这三个方面回顾总结了液相外延生长REBCO(RE=稀土元素)厚膜的研究进展.我课题组发现的高温超导体氧化物YBCO的过热现象直接证实了采用低包晶熔点的YBCO种膜可以生长包晶温度较高的REB-CO,丰富了种膜的选择范围,此现象尤为值得关注.在LPE生长的初始阶段存在种膜的部分溶解、夹杂的形成和与稀土元素种类有关的择优生长等现象,用包括曲率效应和界面能影响的粗化机制可以解释以上现象.因而生长高结晶性的LPE厚膜时选用高品质的种膜甚为重要.为优化生长工艺,须考虑种膜的品质、熔剂中的Ba/Cu比和气氛对Mg的污染和结晶取向,RE离子对Ba的替代等方面问题,以达到获得高质量的REBCO LPE厚膜的目的.

A REVIEW ON THE LIQUID PHASE EPITAXIAL GROWTH OF REBCO THICK FILMS

The recent progresses on the liquid epitaxial growth of REBCO (RE=rare earth) thick films are reviewed. The selection of substrates and seed films, the mechanism of the initial stage of LPE and the optimizing of supperconducting properties are crucial for the application of LPE on REBCO systems. It is demonstrated that the superheating phenomenon found in YBCO thin films in our group make it possible to grow the REBCO superconductor with high peritectic temperature on the a seed film with lower peritectic temperature, and then enlarge the selection of seed films. In the initial stage of LPE, the coarsening mechanism including the curvature effect and interfacial energy can explain many phenomena in the LPE growth, i.e. the partial dissolution of seed films, preferential growth associating with the RE species and the formation of inclusions. Some open questions in the LPE growth, such as Mg contamination, RE/Ba substitution and the crystallinity in the grown thick films, still need to be solved. Seed films with perfect in-plane alignment, the solution with suitable Ba/Cu ratios and the lower oxygen partial pressure are reported to aid to obtain the high-quality REBCO thick films.