High-temperature superconductors (abbreviated high-Tc or HTS) are materials that behave as superconductors at unusually high temperatures. The first high-Tc superconductor was discovered in 1986 by IBM researchers Karl Müller and Johannes Bednorz, who were awarded the 1987 Nobel Prize in Physics "for their important break-through in the discovery of superconductivity in ceramic materials".
Whereas "ordinary" or metallic superconductors usually have transition temperatures (temperatures below which they superconduct) of about 30 K (−243.2 °C), HTS superconductors have been observed with transition temperatures as high as 138 K (−135 °C). Until recently, only certain compounds of copper and oxygen (so-called "cuprates") were believed to have HTS properties, and the term high-temperature superconductor was used interchangeably with cuprate superconductor for compounds such as bismuth strontium calcium copper oxide (BSCCO) and yttrium barium copper oxide (YBCO). However, several Iron based compounds (the Iron pnictides) are now known to be superconducting at high temperatures.
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