GROWTH-MECHANISM OF BI2SR2CACU2OX SUPERCONDUCTING WHISKERS
GROWTH-MECHANISM OF BI2SR2CACU2OX SUPERCONDUCTING WHISKERS
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DOI：
10.1016/0022-0248(94)90103-1
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发表时间：
1994-08-01
影响因子：
1.8
通讯作者：
KAWAI, T
中科院分区：
文献类型：
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作者：
MATSUBARA, I;FUNAHASHI, R;KAWAI, T
Bi2Sr2CaCu2Ox(2212)晶须是通过在O2气流中对熔融玻璃板进行热处理而生长的。除了合适的退火温度和起始成分外，影响晶须生长的因素还有三个。第一种是玻璃前驱体，第二种是玻璃前驱体中Al的存在；虽然2212晶须中不含Al，但在玻璃前驱体中添加Al(约10at%)可以极大地促进晶须的生长。第三个因素是在退火过程中稳定的氧气气流(>；100毫升/分钟)。晶须的生长部位在底部。利用微晶玻璃基板的显微结构和成分分析结果，建立了2212晶须生长机理的模型。根据这一模型，添加Al的玻璃前驱体形成了分布在表面附近的Bi-Sr-Ca-Al-O复合氧化物，作为支撑晶须底部的“刚性骨架”，晶须本身被一层薄薄的富铋相包围，并适合于Bi-Sr-Ca-Al-O相的“微熔炉”。富铋相的成分与与2212相平衡的液态相相同，在退火温度下熔化。晶须的生长是通过2212相从晶须底部的熔体中连续析出而发生的。该模型可称为自承式微顶播机构。
Bi2Sr2CaCu2Ox (2212) whiskers are grown by annealing a melt-quenched glass plate in a stream of O2 gas. Other than the appropriate annealing temperature and starting composition, there are three important factors for the growth of the whiskers. The first is the glass precursor and the second is the presence of Al in the glass precursor; although the 2212 whiskers contain no Al, the addition of Al to the glass precursor (approximately 10 at%) is found to greatly enhance the whisker growth. The third factor is a steady stream of O2 gas (> 100 ml/min) during annealing. The growth site of the whisker is the bottom part. Using the results of a microstructural and compositional analysis of the crystallized glass substrate, a model of the growth mechanism of the 2212 whiskers is devised. According to this model, the Al-added glass precursor forms the Bi-Sr-Ca-Al-O complex oxide distributed near the surface, which acts as a ''rigid skeleton'' to support the bottom part of the whisker, which itself is surrounded by a thin layer of the Bi-rich phase and fits into the ''microcrucible'' of the Bi-Sr-Ca-Al-O phase. The Bi-rich phase has the same composition as the liquid phase equilibrated with the 2212 phase and melts at the annealing temperature. The whisker growth takes place through continuous precipitation of the 2212 phase from the melt at the base end of the whisker. This model can be called a self-supporting micro-top-seeding mechanism.