Pseudobinary phase dicgram and larg high-quality single crystal growth of thallium-based cuprate high temperature superconductors

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Main topics obtained in this study are described below.(1) Pseudobinary phase diagrams of the bismuth-based cuprate high temperature superconductors, which may be similar to that of that of the thallium-based ones, have been clarified by in-situ high temperature X-ray diffraction measurements. stability of a new unstable bismuth cuprate has been also clarified. Crystallization processes of amorphous bismuth-based cuprate have been clarified. The activation energy for the crystallization has been estimated by the time-resolved X-ray diffraction measurements.(2) Vertical-type electric furnace and closed-atmosphere growth technique for the thallium-based cuprate high temperature superconductors have been newly developed. A new growth cell for the thallium-based cuprate high temperature superconductors, which are toxic and have high vapor pressure, has been developed.(3) Large high-quality single crystals of the thallium-based cuprate high temperature superconductors, especially thallium-oxygen double layered cuprates, have been grown. Heavily and slightly overdoped single of the thallium-oxygen double layered cuprate high temperature superconductor have been obtained by annealing under the controlled atmosphere of oxygen partial pressure. The other thallium-based cuprate high temperature superconductors are also now tried to grow.(4) Vortex melting points, irreversible magnetic fields and upper critical fields of the grown crystals have been determined. Vortex behaviors in the cuprate superconductors have been clarified and some new results to resolve a mechanism of the high temperature superconductivity are also obtained. Investigations on the scanning tunneling microscopy, photoemission measurements, de Haas-van Alphen effect measurements using the grown crystals are now going on with many domestic and foreign collaborators.