Microstructure of directionally solidified high-critical-current YBa2Cu3O7-Y2BaCuO5 composites.
Microstructure of directionally solidified high-critical-current YBa2Cu3O7-Y2BaCuO5 composites.
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定向凝固高临界电流YBa2Cu3O7-Y2BaCuO5复合材料的显微组织。
DOI：
10.1103/physrevb.50.7032
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
C. Roucau
中科院分区：
文献类型：
--
作者：
F. Sandiumenge;F. Sandiumenge;S. Piñol;Xavier Obradors;Etienne Snoeck;C. Roucau
The complex microstructure of directionally solidified ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}}$${\mathrm{Y}}_{2}$${\mathrm{BaCuO}}_{5}$ composites having up to 30 vol % 2:1:1 precipitates with sizes down to 0.1 \ensuremath{\mu}m and critical currents above ${10}^{5}$ A/${\mathrm{cm}}^{2}$ at 77 K and zero magnetic field has been investigated through detailed transmission electron microscopy observations. It is shown that samples with a high ${\mathrm{Y}}_{2}$${\mathrm{BaCuO}}_{5}$ concentration display polygonization as a mechanism to relieve stress while only small microcracks occur which are very efficiently stopped by small ${\mathrm{Y}}_{2}$${\mathrm{BaCuO}}_{5}$ precipitates. This crystal polygonization leads to the formation of either sharp or diffuse interfaces within the ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ matrix. In the first case low angle grain boundaries occur which have a minor perturbation of the critical currents, while strongly disordered smooth interfaces are observed in other cases which because of their irregular distribution can only have a minor relevance on the flux-pinning mechanism of these superconductors. Stacking faults are found to be a common defect in the ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ matrix but they are very inhomogeneously distributed thus preventing to establish a clear correlation between their density and critical currents.
The complex microstructure of directionally solidified ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}}$${\mathrm{Y}}_{2}$${\mathrm{BaCuO}}_{5}$ composites having up to 30 vol % 2:1:1 precipitates with sizes down to 0.1 \ensuremath{\mu}m and critical currents above ${10}^{5}$ A/${\mathrm{cm}}^{2}$ at 77 K and zero magnetic field has been investigated through detailed transmission electron microscopy observations. It is shown that samples with a high ${\mathrm{Y}}_{2}$${\mathrm{BaCuO}}_{5}$ concentration display polygonization as a mechanism to relieve stress while only small microcracks occur which are very efficiently stopped by small ${\mathrm{Y}}_{2}$${\mathrm{BaCuO}}_{5}$ precipitates. This crystal polygonization leads to the formation of either sharp or diffuse interfaces within the ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ matrix. In the first case low angle grain boundaries occur which have a minor perturbation of the critical currents, while strongly disordered smooth interfaces are observed in other cases which because of their irregular distribution can only have a minor relevance on the flux-pinning mechanism of these superconductors. Stacking faults are found to be a common defect in the ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ matrix but they are very inhomogeneously distributed thus preventing to establish a clear correlation between their density and critical currents.