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首页> 外文期刊>Key Engineering Materials >Conductivity of Layered Superconducting Crystals in the Normal State: Case of Bi_(2+x) Sr_2 Ca_(1-y) Cu_2O_(8+δ) - Importance of the Oxygen and Cationic Concentrations, Role of Superconductive Fluctuations Above Tc -
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Conductivity of Layered Superconducting Crystals in the Normal State: Case of Bi_(2+x) Sr_2 Ca_(1-y) Cu_2O_(8+δ) - Importance of the Oxygen and Cationic Concentrations, Role of Superconductive Fluctuations Above Tc -

机译：层状超导晶体在正常状态下的电导率：Bi_（2 + x）Sr_2 Ca_（1-y）Cu_2O_（8 +δ）的情况-氧和阳离子浓度的重要性，Tc以上的超导涨落的作用-

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Resistivity anisotropy is well known, in the normal state for all the superconductive strongly layered crystals. It has been studied by many authors for Bi-2212 crystals (of real composition : Bi_(2+x) Sr_2Ca_(1-y)Cu_2O_(8+δ) which can be obtained easily. The first measurements made on Bi-22l2 have shown that the out-of-plane resistivity ρc (resistivity along c) was, at room temperature, about 10~3 to 10~4 times higher than the in -plane resistivity ρab (resistivity in the ab plane), revealing a very high degree of anisotropy of the electrical properties for these crystals. Moreover ρc was given with a semiconducting behaviour and ρab with a metallic one. More recent results have shown that ρc could be metallic and that the ρc/ρab ratio could be greatly reduced, going along with an increase of the density of charge carriers in the valence band, itself related to an increase of the oxidation degree of the crystal (increase of δ). It was shown also that Tc is directly related to the oxygen concentration, a maximum value Tc_(max) of Th being associated to an optimal δ_i value of δclose to 0.25; Tc_(max) is also probably obtained for an optimal cationic composition including an excess of Bi and probably a lack of Ca. From our own results Tc_(max) can reach 99k going along with a metallic behaviour along c. Out of the interesting case of highly oxygen doped crystals, the out-of plane resistivity of Bi-2212 crystals is semiconducting like. But the increase of resistivity with reducing temperature, above Th, is quicker than expected from the Arrhenius law. This point is
机译：在所有超导强层晶体的正常状态下，电阻率各向异性是众所周知的。许多作者研究了Bi-2212晶体（实际成分为Bi_（2 + x）Sr_2Ca_（1-y）Cu_2O_（8 +δ），该晶体很容易获得。在Bi-22l2上进行的首次测量为结果表明，在室温下，面外电阻率ρc（沿c的电阻率）比面内电阻率ρab（ab平面中的电阻率）高约10〜3至10〜4倍，显示出很高的这些晶体的电学性质的各向异性程度，此外，ρc具有半导电性，ρab具有金属性，最近的结果表明，ρc可能是金属的，ρc/ρab的比值会大大降低。随着价带中载流子密度的增加，其本身与晶体的氧化程度的增加（δ的增加）有关；还表明，Tc与氧浓度直接相关，最大值Tc_ Th的（max）与接近0.25的δ的最佳δ_i值相关; Tc_（对于最佳的阳离子组成（包括过量的Bi和可能缺乏的Ca），也可能获得最大的摩尔数。从我们自己的结果来看，Tc_（max）可以达到99k，并且沿着c会有金属行为。在高氧掺杂晶体的有趣情况下，Bi-2212晶体的面外电阻率像半导体一样。但是，随着温度的降低，电阻率在Th之上的增加比Arrhenius定律所预期的要快。这一点是

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