分层式前驱坯体对YBCO单畴块材生长和磁通性能的影响

Influence on Processing and Magnetic Flux Properties of Single Grain YBCO Fabricated from Layered Precursor Powders

Y-Ba-Cu-O(YBCO)单畴块材通常是由统一分布的YBa2Cu3O7-δ(Y123)和Y2Ba CuO5(Y211)前驱坯体制备的。然而研究表明熔融生长的超导块材中Y211相粒子的浓度随着远离籽晶显著增大,造成Y211相粒子的积聚以及限制单畴块材的超导性能。本文通过顶部籽晶熔融织构法(TSMTG)利用分层式前驱坯体制备了φ23 mm×9 mm的YBCO单畴块材,并在生长形貌、微结构以及磁通俘获性能方面与常规方法制备的同尺寸YBCO单畴块材做了对比研究。研究结果显示,使用分层式前驱坯体制备的YBCO单畴块材生长得更充分,Y211相粒子的平均粒径更小、分布更均匀,并且在磁通俘获性能上有了显著的提高,同时具备高对称性的磁通分布和强磁通俘获能力,在77 K环境下最大磁通俘获场高达0.91 T。该结果对进一步提高YBCO超导块材的性能具有很好的参考价值。

The fabrication of single domain Y-Ba-Cu-O（YBCO） bulk superconductors usually involves precursor pellets that contain a uniform distribution of YBa2Cu3O7-δ（Y123） and Y2 Ba CuO5（Y211） compounds. However, the concentration of Y211 phase particles in the fully melt processed superconducting bulk increases significantly with distance from the seed, leading to accumulation of Y211 phase particles and degradation of superconducting properties. By top seeded melt texture growth（TSMTG） process, single domain YBCO bulk superconductors at about 23 mm in diameters, and 9 mm in thickness were fabricated from layered precursor pellets and conventional precursor pellets, respectively. The growth morphology, microstructure and magnetic flux properties of both layered and conventional pellets were comparatively studied. The experiments suggest that the layered precursor pellets allow a sufficient growth in c growth sector, a more uniform distribution of Y211 phase in the matrix and a significant enhancement of the trapped field. Thus for the layered pellets, a trapped magnet field of 0.91 T is achieved at 77 K and the flux distribution is also of high symmetry. The present results are very valuable for further improving the properties of YBCO bulk superconductors.