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采用固相反应法制备名义组分为 Bi_3Sr_2Ca_2Cu_3Oy(3223),Bi_2Sr_2Ca_3Cu_3Oy(2223),Bi_2Sr_2Ca_6Cu_7Oy(2267)的纯 Bi-Sr-Ca-Cu-O 体系的样品.对样品进行了物相分析.电阻率和磁化率测量,结果表明:①组分为3223,2223样品的零电阻温度分别为110.5K 和101K,样品的零电阻温度 T_(ce)与其高 T_c 相的含量并无十分明显的联系;②样品中富 Bi 比富 Ca 更有利于提高零电阻温度.作者认为,样品中富 Bi 有利于改善晶界的导电性能,是提高零电阻温度的主要因素. 相似文献
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采用固相反应法制备名义组分为 Bi_3Sr_2Ca_2Cu_3Oy(3223),Bi_2Sr_2Ca_3Cu_3Oy(2223),Bi_2Sr_2Ca_6Cu_7Oy(2267)的纯 Bi-Sr-Ca-Cu-O 体系的样品.对样品进行了物相分析.电阻率和磁化率测量,结果表明:①组分为3223,2223样品的零电阻温度分别为110.5K 和101K,样品的零电阻温度 T_(ce)与其高 T_c 相的含量并无十分明显的联系;②样品中富 Bi 比富 Ca 更有利于提高零电阻温度.作者认为,样品中富 Bi 有利于改善晶界的导电性能,是提高零电阻温度的主要因素. 相似文献
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采用固相反应法制备了Y2O3施主掺杂的92 mol%BaTiO3-8 mol%(Bi1/2Na1/2)TiO3(BBNT8)高温无铅正温度系数电阻(positive temperature coe?cient resistivity,PTCR)陶瓷.利用透射电镜观察材料的显微结构,发现陶瓷的显微结构主要包括晶粒和晶界两部分,观察不到明显的壳层结构.进一步利用交流阻抗谱研究了陶瓷的宏观电学性能,发现陶瓷的总电阻是晶粒和晶界两部分的贡献,而晶粒电阻很小,在居里温度以上变化不大,材料的PTCR效应主要是晶界部分的贡献.当温度高于居里温度时,随着温度的升高,晶界介电常数逐渐减小,导致势垒增加,晶界电阻增大,从而产生正温度系数效应.最后,通过测试材料的介电频谱特性,研究计算了陶瓷的室温电阻率. 相似文献
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制备了Bi7Ti4NbO21,Bi4Ti3O12及Nb掺杂Bi4Ti3O12(Nb-Bi4Ti3O12)层状结构铁电陶瓷材料.结合Nb-Bi4Ti3O12的介电温谱和退极化实验结果,研究了Bi7Ti4NbO21的晶体结构对其介电、压电性能的影响.高分辨透射电镜结果表明,在Bi7Ti4NbO21中,沿着c轴方向,(Bi2Ti3O10)^2-和(BiTiNbO7)^2-。两个类钙钛矿层分别与(Bi2O2)^2 层叠加堆积而成.这种晶体结构决定了Bi7Ti4NbO21的介电温谱在668℃和845℃出现介电双峰.结合极化样品的退化实验分析,说明材料在这两个温度附近发生了铁电一铁电相变、铁电一顺电相变,分别是(Bi2Ti3O10)^2-和(BiTiNbO7)^2-层状结构发生微观结构相变的结果.在退极化过程中,由于受热时钙钛矿层内空位引起的缺陷偶极子的定向排列受到破坏,引起材料部分退极化,表现为300℃热处理后Bi7Ti4NbO21的压电活性降低了10%,显示了室温下材料的压电性能来源于自发极化的固有电偶极子和缺陷偶极子的共同贡献. 相似文献
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用光电子能谱研究了(Bi.Cd)Sr_2(Ln,Ce)_(?)Cu_2O_y的电子结构,以及其与铝之间的反应.芯能级结果表明:(Bi,Cd)Sr_2(Ln,Ce)_(?)Cu_2O_y系列中n=1,2和3三种材料的结果基本一致,并且类似其它超导材料中相同元素的芯能级结果.在(Bi,Cd)Sr_2(Ln,Ce)_(?)Cu_2O_y与铝的界面处,铝与(Bi,Cd)Sr_2(Ln,Ce)_(?)Cu_2O_y中的元素发生强烈反应,Bi—O,Sr—O和Cu—O键受到破坏,铜的价态从+2变为+1,并且同时伴随着超
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利用等温原位电阻测量和热重分析等方法,深入研究Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_(10+5)超导材料在不同温度下氧气和空气中的退火行为,发现电阻率和重量均随退火时间单调增加,最后趋于平衡.同时观察到类Ca_2PbO_4杂相析出,调制结构由Pb型(波矢q=β_1b)逐渐转变为Bi型(q=β_2b+c),适量的杂相析出使T_c(0)有所增高.根据电阻率变化的规律判断,类Ca_2PbO_4杂相析出受2223母相Bi_2-O_2层中Pb~(+2)离子的二维扩散控制,求得Pb~(+2)离子
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采用固相反应法合成了名义组份为Bi_(2-x)Pb_xSr_2Ca_2Cu_3O_y(x=0.30;0.35;0.40;0.45)的样品。对样品进行了物相和结构分析,同时测量了电阻-温度关系和直流磁化率。结果表明:x=0.35的样品为单相材料,X射线相分析和电子衍射表明其相结构类似2223相,为四方结构,其晶格常数为a=b=5.414A,c=37.106A,且沿a,b两个方向都观察到调制结构。电阻和直流磁化率测量结果显示:在温度高于50K以上,仅存在一个 107K超导相。此外,单相材料的制备条件(组分、烧结温度、室温下淬火及淬火速率)非常苛刻。如同1-2-3相材料一样,氧含量不仅影响样品的成相规律、零电阻温度,而且还严重影响其正常态的输运性质。 相似文献
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Bi-2212单晶本征Josephson结的制备及其非线性行为 总被引:1,自引:0,他引:1
采用自助熔剂固态反应法制作了Bi2Sr2CaCu2O8+x单晶,使用光刻蚀和Ar离子刻蚀技术在Bi-2212单晶表面制作了台阶结构的Josephson本征结.用三引线和四引线法分别测量了该样品零场下c轴方向的电阻-温度(R-T)关系和恒定温度(14.4K)时的I-V特征曲线.I-V曲线具有典型的多分支非线性行为,并对该实验结果进行了讨论. 相似文献
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《Physica C: Superconductivity and its Applications》1999,311(1-2):65-74
Nanometer SiC particles were added to (Bi,Pb)2Sr2Ca2Cu3Ox (Bi2223) precursor powders and the powders were transformed into silver-sheathed superconducting tapes by the standard powder-in-tube (PIT) technique. The influence of SiC on the melting temperature, high-Tc (Bi2223) phase formation, microstructure and transport property of the tapes was studied by means of DTA, XRD, SEM/EDX, electrical and magnetic measurements. The results showed that SiC addition lowered the melting temperature of the superconductor powders and consequently, decreased the optimum sintering temperature of the tapes. However, the addition did not affect the Bi2223 phase formation and critical temperature (Tc) of the tapes up to 1.00 wt.% of SiC. Most importantly, the addition of a small amount of SiC (0.15 wt.%) improved the critical current (Ic) and Ic behavior in magnetic field as a result of the enhancement in density, grain alignment, grain connectivity and flux pinning of the tapes. 相似文献
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本文对工频过电流冲击下准绝热环境中的Bi-2223/Ag不锈钢加强多芯带的失超及恢复特性进行了实验研究.通过实验测量了在液氮温度(77K)、自场下Bi-2223/Ag超导带在幅值为100 A至1 015 A,时间为300 ms的工频电流冲击下,超导带材两端的电压,电流及带材表面温度的变化,得到冲击期间各参量的变化规律.另外,还比较了冲击电流相同、正常载流不同时,带材的温升及失超恢复时间,结果表明正常载流大时,则带材温升较高,失超恢复时间长.正常载流为60A<0.5Ic时,带材失超恢复时间为冲击时间的21倍. 相似文献
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H. Utsunomiya T. Sakai Y. Saito T. Matsuo 《Physica C: Superconductivity and its Applications》1995,250(3-4):340-348
Silver-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox (Bi(2223)) tapes were fabricated by the “oxide-powder-in-tube” technique. After the tapes were shaped and sintered, an additional cold rolling and a re-sintering were applied in order to enhance the critical current density Jc. The influence of the additional rolling conditions (roll diameter, number of passes, lubrication) on the Jc (77 K, 0 T) was made clear. The influence of the sintering conditions (temperature, heating rate) on Jc was also investigated. As for the rolling conditions, a small redundant shear deformation or a small contact angle leads to a good grain alignment, texturing, and a higher Jc value. As for the temperature of the first sintering, 1113 K is superior to 1118 K because of the volume fraction of the Bi(2223) phase. 相似文献
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Bi2 2 2 3银包套超导带材是研制高温超导磁体和高温超导强电应用的基础。文中就对高温超导磁体最大运行电流有重要影响的 Bi2 2 2 3银包套带材侧向弯曲形变进行了初步探讨 ,就不同的侧向弯曲率对超导带载流能力的影响进行了实验测试 ,并提出了提高 HTS磁体最大运行电流的方法。 相似文献
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Temperature dependence of electrical conductivity and thermoelectric power are presented for In and Pb doped Bi + 8.28 at
% Sb quenched tapes between 77 and 300K. The results are explained in terms of model for disordered semiconductors. Analysis
of our data on electrical conductivity indicates the presence of a temperature independent part and a strongly temperature
dependent part. While theT independent part originates from band conduction, theT dependent component could be understood considering the presence of localized states. Thermoelectric figure-of-merit of these
tapes are also measured at 300K, which shows a large enhancement (∼40%) over that reported earlier on thin Bi-Sb films. This
suggests that doped Bi-Sb quenched tapes may be considered as a candidate for material in producing economic and light weight
thermoelectric devices. 相似文献