Hg系新高Tc超导体研究

STUDY ON THE NEW HIGH-TC SUPERCONDUCTORS IN THE Hg-Ba-Ca-Cu-O SYSTEM

我们制备了新高ＴｃＨｇ—Ｂａ—Ｃａ—Ｃｕ超导氧化物系，并用Ｘ—ｒａｙ衍射、ＴＥＭ、磁化率及电阻等实验测量对它们进行了研究，由ＴＥＭ观察，证实了在ＨＢＣＣＯ系中存在Ｈｇ—１２０１相，Ｈｇ—１２１２相和Ｈｇ—１２２３相．用高－Ｑ振动子技术，对ＨｇＢａ２ＣｕＯ４＋ｙ样品作了与磁通点陈运动有关的力学测量，从而估计出该样品的不可逆线的形状．我们还对Ｈｇ—１２２３样品作了事后退火处理研究，在氧气中退火可使该样品的Ｔｃ略有增高，这些结果表明Ｈｇ－１２２３样品的超导相可能处在微弱的“ｕｎｄｅｒ－ｄｏｐｅｄ”态．

The high temperature superconducting HgBa2 Can-1Cun O2n+2+y(Hg-12[n-1]n) system has been produced and studied by X-ray diffraction, transmission electron microscopy, susceptibility and resistivity. We confirmed that there were Hg-1210,Hg-1212 and Hg-1223 phases in the HBCCO system according to transmission electron microscopic (TEM) observations. From mechanical measurements of flux-lattice melting in sample using the high-Q oscillator technique, we estimated the location of the irreversibility line Hirr (T) in the magnetic phase diagram of the material. Particularly,samples containing superconducting HgBa2Ca2Ca2O3+y(Hg-1223) as the dominant phase have been investigated by resistivity and susceptibility measurements. As-sintered samples o f the Hg-1223 superconductors were annealed in flowing oxygen. The superconducting critical temperature To of the samlpe increased after annealing. This result implies that Hg-1223 superconducting phase in the as-sintered sample was in a slightly ' under-doped 'state.