论文部分内容阅读
报导了用熔融定向凝固工艺制备的有织构YBCO超导体的微结构变化及其特性。将YBCO坯料加热到1050—1120℃,分解成Y_2BaCuO_5(211)和液相(Ba-Cu-O),然后在50℃/cm的温度梯度下,慢速移动样品重新合成YBCO超导体。X光衍射结果证实,熔融样品具有较强的c轴织构。扫描电镜观察表明,熔融后晶粒形貌发生了显著变化:YBCO晶粒由原烧结块材的随机排列变为一致取向或局部取向排列的片状组织。熔融样品的J_c(77K,0T,>10000 A/cm~2)值比烧结块材J_c(750A/cm~2)值提高近两个数量级,在1T(H⊥I_c)下,J_c值达5790 A/cm~2。而且J_c随磁场增加而下降的趋势变平缓。
The microstructural changes and their properties of textured YBCO superconductors prepared by melt directional solidification were reported. The YBCO billets were heated to 1050-1120 ℃ and decomposed into Y_2BaCuO_5 (211) and liquid phase (Ba-Cu-O). The YBCO superconductor was then synthesized slowly by moving the sample slowly at a temperature gradient of 50 ℃ / cm. The results of X-ray diffraction confirmed that the melted sample has a strong c-axis texture. Scanning electron microscopy showed that the morphology of the melted grains changed significantly: the YBCO grains changed from the random arrangement of the original sintered agglomerates to the uniformly oriented or locally oriented lamellar structures. The value of J_c (77K, 0T,> 10000 A / cm ~ 2) in molten sample increased by nearly two orders of magnitude compared with the value of 750_C / 2 in sintered mass, and the value of J_c reached 5790 at 1T (H⊥_c) A / cm ~ 2. Moreover, the trend of J_c declining with increasing magnetic field becomes flat.