Relationship between Carrier Concentration and Superconducting Transition Temperature in Bi-Sr-Ca-Cu-O Superconductor

  • Kim, Myung Chul (Department of Materials Science and Engineering, KunSan National University) ;
  • Park, Soon Ja (Department of Inorganic Materials Engineering, Seoul National University)
  • Received : 1992.06.01
  • Published : 1992.06.25

Abstract

$Bi_2Sr_2Ca_2Cu_3Oy$-based superconductor phases were synthesized by the wet process using acetate precursors. Superconducting transition temperature ($T_c$) was determined from both measurements of electrical resistivity and magnetic susceptibility for the samples which were sintered at the temperatures of $850^{\circ}C$, $860^{\circ}C$, and $870^{\circ}C$ for 40 hours, respectively. The values of carrier concentration from Hall measurements were compared with $T_c$ data as a function of the sintering temperature. The formation mechanism of the superconducting phase was tentatively discussed on a basis of the distribution profile concept of the carrier concentration and the amount of superconducting phases in a ceramic bulk. This explanation may be supported by the experimental results of correlation between the relative amount of superconducting phases and the difference of $T_c$ values between superconducting onset temperature and cutoff temperature at each sintering temperature.

초산염(acetate)을 출발원료로 하여 $Bi_2Sr_2Ca_2Cu_3Oy$계 단일상 고온초전도체를 합성하려 하였으며 그 초전도상의 형성과정을 초전도전이온도 $T_c$ 및 전하나르게 농도와의 상관관계로부터 설명하고자 하였다. 초전도전이온도 $T_c$는 전기저항밀도 및 자화율을 측정하여 결정하였다. 시료로는 상기의 초전도체 출발조성물의 하소분말에 대해 $850^{\circ}C$, $860^{\circ}C$, 그리고 $870^{\circ}C$에서 40시간 동안 공기 중 열처리한 것을 이용하였다. 전하나르게농도는 홀계수를 측정하여 구하였다. 열처리과정 중의 초전도체 형성과정을 세라믹벌크내에 형성된 초전도체의 양 및 전하나르게농도 분포의 상관관계로부터 설명하였다.

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