Phase separation and growth in as-grown superconducting La2CuO4+delta single crystal
As-grown superconducting single crystals of La2CuO4+delta have been obtained for the first time by the flux method. Its morphology is remarkably different from that of the insulating crystals usually grown by the flux method. A reversible phase separation occurs in the temperature range of 270-190 K...
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| Format: | Conference item |
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2001
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| Summary: | As-grown superconducting single crystals of La2CuO4+delta have been obtained for the first time by the flux method. Its morphology is remarkably different from that of the insulating crystals usually grown by the flux method. A reversible phase separation occurs in the temperature range of 270-190 K. T-c reaches a constant value of similar to 28 K after a constant temperature treatment, which indicates completion of the phase separation. T-c further increases to a higher value by subsequent cooling, which suggests phase ordering or growth. Supersaturation of the oxygen-rich phase seems to be the thermodynamic driving force. The growth mainly occurs from 260 to 200 K. and is dependent on the temperature and the cooling rate. T-c similar to 34 K is achieved with a temperature program above 200 K. No significant T-c increase is observed by further cooling below 200 K. A phase diagram is proposed to describe the phase separation and growth., by which a composite structure is self-assembled in the duplex single crystal. (C) 2001 Elsevier Science B.V. All rights reserved. |
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