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JOINING OF UNIDIRECTIONALLY SOLIDIFIED SUPERCONDUCTING OXIDE AND SILVER AND EVALUATION OF ITS INTERFACE CHARACTERISTICS

单向凝固超导氧化物与银的接合及其界面特性评价

基本信息

批准号：
05650733
负责人：
MORI Nobuyuki
金额：
$ 1.47万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05650733/
关键词：
YBCO Superconducting oxide Silver Joining Interface resistivity Interface reaction Solidification Peritectic 酸化物超伝導体

项目摘要

Two fabrication methods were investigated to develop the low resistivity joints of silver and Y-Ba-Cu-O superconducting oxide (YBCO) with the columnar crystal structure of 123 phase (YBa_2 Cu_3O_<7-X>) , which was obtained by unidirectional solidification from liquid+211 (Y_2BaCuO_5) phases. One of the methods was a solid state processing by the hot-press to make solid silver/YBCO joint, in which no detectable interaction layr was formed. The interface resistivity (rhoc) at 77K measured by the four-prove method decreased with the increase in joining temperature (T) or joining pressure (P) , and the minimum value : rhoc=2*10^<-12>OMEGA・m^2 was obtained when the joining conditions were P=32MPa, T=873K,t=3600s.Another method was a liquid state processing by using molten silver, in which the remarkable reaction layr was formed at the interface. Since the reaction was caused by the decomposition of 123 phase to liquid+211, the reaction layr was recovered to 123 phase by slow cooling and sol … More idification. In this case, rhoc remarkably decreased by the recovering treatment, and the minimum value was as low as about 10^<-12>OMEGA・m^2, Which satisfied the stability criteria for composite wire. Further, to study the structure controll of YBCO substrate, the growth mechanism of 123 columnar crystal was analyzed, which grew with a facet interface from liquid+211 through a peritectic reaction with solute diffusion in the liquid. The following relation was conducted between 123 growth rate (R) and undercooling (DELTATpc=Ti-Tp, Ti : interface temperature, Tp : peritectic temperature) by the analysis of kinetics for 123 columnar crystal growth : R=(Ca/eta)・{(ML・DELTATpc+DELTACrc)/(Tp/m_<L123>+Cf・Tp/m_<L211>)}^2, where Ca and Cf are constants, eta is the viscosity, ML=1/m_<L123>-1/m_<L211>, m_<L123> and m_<L211> are respectively the slope of liquidus of 123 and 211, DELTACrc is the change in equilibrium solute concentration caused by the surface energy of 211 particle at the 123 freezing front. This relation agreeed well with the experimental results. The transition of 123 crystals from columnar to equiaxd structure was successfully simulated by using the above R-DELTATpc relation and the experimental undercooling (DELTATp) for the nucleation of 123 crystals. Less

本文研究了两种制备方法，制备了由液态+211（Y_2BaCuO_5）相定向凝固得到的123（YBa_2Cu_3O）相柱状晶结构的银和Y-Ba-Cu-O超导氧化物（YBCO）低电阻率接头<7-X>。其中一种方法是采用热压固相工艺制备固态银/YBCO接头，接头中没有可检测到的相互作用层。采用四点法测得的77 K下的界面电阻率（rhoc）随连接温度（T）或连接压力（P）的增加而减小，在<-12>P= 32 MPa，T= 873 K，t= 3600 s时，rhoc达到最小值：rhoc=2*10^Ω·m^2。在界面处形成了显著的反应层。由于反应是由123相分解为液相+211引起的，因此通过缓慢冷却和溶胶-凝胶法使反应层恢复为123相， ...更多信息身份化在这种情况下，通过回复处理，rhoc显著降低，最小值低至约10^<-12>Ω·m^2，满足复合丝的稳定性标准。进一步，为了研究YBCO衬底的结构控制，分析了123柱状晶体的生长机制，该晶体是在+211液相中通过溶质扩散的包埋反应生长的，具有小面界面。通过对123柱晶生长动力学的分析，得到了123柱晶生长速率（R）与过冷度（Δ TATpc =Ti-Tp，Ti：界面温度，Tp：过冷度）的关系式：R=（Ca/eta）·{（ML·Δ TATpc + Δ TACrc）/（Tp/m_<L123>+Cf·Tp/m_<L211>）}^2，其中Ca和Cf为常数，eta为粘度，ML=1/m_<L123>-1/m_<L211>，m_<L123>和m_<L211>分别为123和211的液相线斜率，Δ ACrc是由在123冻结前沿处的211粒子的表面能引起的平衡溶质浓度的变化。该关系式与实验结果符合得很好。利用上述R-DELTATpc关系和123晶体形核的实验过冷度（DELTATp）成功地模拟了123晶体从柱状晶向等轴晶的转变。少