Electrochemical crystal growth of superconducting cuprates and copper-less oxides

本研究旨在发展低温合成氧化物超导体单晶的新技术。本文主要研究了用电化学方法合成铜酸盐和无铜氧化物超导材料。该研究包括三个项目;1。不同组分Ba_ K_xBiO_3晶体的合成及输运性质的表征<1-x>.超导铜氧化合物单晶的合成与表征.研究新的无铜超导氧化物。项目的结果如下：项目1：通过精确的电阻率和霍尔效应测量，揭示了材料的输运性质，晶体具有广泛的组成范围。它示出，特别是，输运性质强烈相关的晶体相的变化，包括氧的组合物的超导电性的影响。此外，还研究了Ba_<1-x>K_xBiO_的能带结构。 ...更多信息 3已通过与东京大学理学部合作的X射线吸收测量直接表征。项目二：成功地生长了La_2CuO_（4+ δ）和Nd_<2-x>Ce_xCuO_（4 + δ）体系的晶体，表明电化学方法是一种独特的铜酸盐超导晶体生长方法。特别地，La_2CuO_（4+ δ）在生长态下不经任何高压氧热处理就显示出超导电性，并且通过电化学方法生长的晶体中含有足够的氧，从而显示出超导电性。我们已经成功地生长了BaRuO_3等晶体，并对其性能进行了表征。除此之外，我们还开发了一种新的电解池法来合成氧化物晶体。这种方法是利用电极上出现的电动势进行晶体生长。将该方法应用于Ba_ K_xBiO_3晶体的合成<1-x>，证实了该方法可以生长出高质量的晶体。少

This study has been performed to develop new technique to synthesize single crystals of oxide superconductors at low temperature. The study has focused on the synthesis of superconducting cuprates and copper-less oxides by means of electrochemical method. The study consists of three projects ;1. Synthesis and characterization of transport properties of Ba_<1-x>K_xBiO_3 crystals with various compositions.2. Synthesis and characterization of single crystal of superconducting cuprates.3. Search of new copper-less superconducting oxides.The results of the projects are as follows ;Project 1 : Transport properties of the material have been revealed by means of precise resistivity and Hall-effect measurements for the crystal with wide range of composition. It is shown, in particular, that the transport property correlates strongly to the changes in the crystallographic phase and that the composition including oxygen affects to the superconductivity. In addition, band scheme of Ba_<1-x>K_xBiO_ … More 3 has been characterized directly by X-ray absorption measurement in the collaboration with Dept.of Science, Tokyo Univ..Project 2 : Crystals of the La_2CuO_<4+delta> and Nd_<2-x>Ce_xCuO_4 systems have been successfully grown, and it is shown that the electrochemical method is a unique method for the crystal growth of superconducting cuprates. In particular, La_2CuO_<4+delta> shows superconductivity in as-grown state without any heat treatment in high pressure oxygen, and it is revealed that the crystals grown by the electrochemical method contain enough oxygen to show superconductivity.Project 2 : Synthesis of oxides containing Nb, Mo, and Ru has been performed. Crystals such as BaRuO_3 have been successfully grown, and characterization of their properties is in progress.In addition to the projects, we developed new "Electrolysis-cell method" for the synthesis of oxide crystals. In this method electromotive force appeared at the elettrodes is used for the crystal growht. The method was applied to the synthesis of Ba_<1-x>K_xBiO_3 crystal, and it is confirmed that high quality crystals can be grown by the method. Less