Study on the Interrelation Between Crystal Growth, Phase Transition and Properties of High Tc Superconductors.

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1. Flux growth of high Tc superconductors (123 phase)(1) Various kinds of 123 single crystals were grown by changing the rare earth elements, such as, Nd, Eu, Gd, Dy, Er, etc. The composition of the flux was varied by changing the composition ratio of CuO and BaO. But this did not bring new results.(2) The deficiency of oxygen within the 123 single crystals was improved by treating the crystals in a molten CrO_3 salt.(3) Traveling solvent floating zone method (TSFZ) using a mirror image was employed for growing 123 phase and Bi system crystals. But it was not successful to grow a large single crystal, in stead, they became several single crystals.2. Liquid phase epitaxial growth of Bi system crystals on Mgo was tried but it was not possible to observe an epitaxial effect.3. The temperature range of the liquid coexisting with so-called 110K phase of Bi system crystal was directly measured under a microscope, and pseudo-binary phase diagram with the end members Bi_2(SrCa)O_4 and (SrCa)CuO_2 was established.4. Optical microscopic investigation of as-grown crystals was made using a phase-contrast microscope which is not disturbed by polarization of reflected light from crystals surfaces.