功能材料雙語-電功能材料-展示頁
2025-01-21 15:39本頁面
【正文】 conductivity is 107~108 S/m。 sliver（ 107 S/m ）、 copper（ 107 S/m ） aluminum （ 107 S/m ） （ 2） alloy. the conductivity is 105~107 S/m。s notebook was found. Definition of superconductors ?Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magic fields occurring in certain materials when cooled below a characteristic critical temperature. Elementary properties of superconductors exactly zero resistivity（ 絕對零電阻 ） Experimental evidence points to a current lifetime of at least 100,000 years. Meissner effect（ 邁斯納效應 ） the plete ejection of magic field lines from the interior of the superconductor as it transitions into the superconducting state ejection of magic field lines ?The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics. ?The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In ordinary conductors, such as copper or silver, this decrease is limited by impurities（ 雜質(zhì) ） and other defects（ 缺陷 ） . Even near absolute zero, a real sample of a normal conductor shows some resistance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. critical temperature Tc， critical magic field Hc， critical current Jc（ 臨界溫度 、 臨界磁場 、 臨界電流密度 ） the characteristics of superconductivity disappear when the temperature Tc is higher than the critical temperature Tc。 maglev trains（磁懸浮列車） 近日，國家“十三五”重點研發(fā)計劃 《 現(xiàn)代軌道交通專項 》 啟動時速 600公里高速磁懸浮交通和時速 200公里中速磁浮交通研發(fā)項目 superconducting electric power transmission 未來超導體汽車 尋找現(xiàn)實中的哈利路亞山 ——室溫超導體 semiconductor ?has electrical conductivity between that of a conductor such as copper and that of an insulator such as glass（ σ＝ 107～ 104） ?Negative temperature coefficient （ 負 的 電 阻 溫 度 系數(shù) ） : thermal conductivity or electrical resistivity of a semiconductor lowers with increasing temperature, which is opposite to that of a metal. semiconductor useful properties: ?passing current more easily in one direction than the other。 ? sensitivity to light or heat（ 對光 /熱敏感 ） So, electrical properties of a semiconductor material can be modified（ 修飾 ） by controlled addition of impurities（ 雜質(zhì) ） , or by the application of electrical fields or light. basic concepts: In solidstate physics, the electronic band structure (or simply band structure) of a solid describes those ranges of energy that an electron within the solid may have and ranges of energy that it may not have (called band gaps or forbidden bands)帶隙或禁帶 . （ 1）
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