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|Section2= |Section3= |Section7= |Section8= }} Yttrium barium copper oxide, often abbreviated YBCO, is a family of crystalline chemical compounds, famous for displaying "high-temperature superconductivity". It includes the first material ever discovered to become superconducting above the boiling point of liquid nitrogen (77 K) at about 90 K. Many YBCO compounds have the general formula YBa2Cu3O7-x (also known as Y123), although materials with other Y:Ba:Cu ratios exist, such as YBa2Cu4Oy (Y124) or Y2Ba4Cu7Oy (Y247). ==History== In April 1986, Georg Bednorz and Karl Müller, working at IBM in Zurich, discovered that certain semiconducting oxides became superconducting at relatively high temperature, in particular, a lanthanum barium copper oxide which becomes superconducting at 35 K. This oxide was an oxygen deficient perovskite-related material that proved promising, and stimulated the search for related compounds with higher superconducting transition temperatures. In 1987, Bednorz and Müller were jointly awarded the Nobel Prize in Physics for this work. Following Bednorz and Müller's work, in 1987 M.K. Wu and Paul Chu and their graduate students Ashburn and Torng at the University of Alabama in Huntsville, discovered that YBCO has a critical temperature (''T''c) of 93 K. (The first samples were Y1.2Ba0.8CuO4.) That paper led to rapid discovery of several new high temperature superconducting materials, ushering in a new era in material science and chemistry. YBCO was the first material found to become superconducting above 77 K, the boiling point of liquid nitrogen. All materials developed before 1986 became superconducting only at temperatures near the boiling points of liquid helium (''T''b = 4.2 K) or liquid hydrogen (''T''b = 20.28 K) — the highest being Nb3Ge at 23 K. The significance of the discovery of YBCO is the much lower cost of the refrigerant used to cool the material to below the critical temperature. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「yttrium barium copper oxide」の詳細全文を読む スポンサード リンク
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