超導接合技術為多塊超導單晶粒以熔融製程進行結合，形成未具有高角度晶界之大尺寸單晶粒塊材，提升擄獲磁場能力，同時增加單晶形狀上的多元性。本研究利用高溫熔融超導塊材表面的方式，藉由控制製程溫度、時間及降溫速率，以內部未破壞之Y123單晶粒母材作為晶種以重新成長，維持整體單晶粒形貌並達接合目的，避免接合劑及液相殘留現象對於超導性質的影響。
製程上包含多段式及單段式曲線兩種設定模式。多段式曲線為利用升溫，降溫，升溫的方式使塊材反覆熔融表面區域以構成接合良好且可相對完整保留內部單晶粒母材之製程。本團隊發現在相對低溫的參數下，多段式曲線確實可避免液相殘留的發生，並得到良好再成長(re-growth)的單晶面，於(001)/(001)方位接合樣品中擄獲0.15KG的單峰磁場(並無出現弱接點效應)，但樣品接合比例低(61%)，塊材機械性質差，不利於後續發展及應用。相對於此，以單段式曲線增加持溫時間雖然會造成熔融區域較深，但較多的液相有效地促進原子擴散，成功將接合比例提升至77%，並於(001)/(001)方位接合樣品之擄獲磁場強度提升至0.45KG。
以單段式最佳化曲線進行a-b平面接合（包含(100)/(100)及(110)/(110)方位），可得到單峰或是類單峰的擄獲磁場型貌。於尺寸為17mm ×17mm之a-b平面接合樣品可擄獲1.08KG的磁場(77K,1T)，已接近相等面積單晶粒塊材之擄磁強度(~1KG)。以二維XRD進行極圖線性掃描(line scan)之分析，發現單峰及類單峰樣品有極佳的角度耦合情況，推測並非晶格取向差異造成的弱接點效應。藉由微結構分析，於類單峰形貌樣品之接合界面發現局部Y211缺乏區，此區域認為與液相流動和晶體再成長過程中的排推效應(push trap effect)相關。Y211與Y123之界面缺陷為有效釘扎中心(pinning center)，故Y211缺乏區將無法有效釘扎磁場，使擄獲磁場強度下降。本研究針對樣品不同區域之Y211比表面積與其釘扎能力(Jc)作比較，證實為Y211缺乏區造成擄磁類單鋒形貌。
考量樣品接點機械強度較弱，本研究將接合樣品以碳纖維布進行強度強化。由三點抗彎量測可發現，披覆碳纖維布之接合樣品其接點強度可由12.8Mpa上升至72.7Mpa，且於45K,外加磁場3T的情況下可擄獲5KG的高磁場而不產生破裂。

Joining technology of superconductor is a method to connect multiple single grains together by melting process, and form a larger single grain bulk without high angle grain boundary. Using this technology it not only improves the trapped field ability of superconductor, but also increases the diversity of the shape. In this study, entire surface of joint samples are melted by well control of the process temperature, holding time and cooling rate, and the original bulk inside the melting zone is taken as seed to re-grow to a single grain. It should be noticed that this method avoids addition of join agent and prevents the residual liquid phase, which may weaken the superconductivities.
Two kinds of joint profile are used in the experiments: multi-step melting process and single-step melting process. In multi-step process, by repeating rising and cooling processes the surface of jointing bulks are melted and form good joint at the same time protect the original bulk.The low temperature parameters displayed single cone shape trapped field distribution(0.15KG) at (001)/(001) joint samples with well re-growth grain quality and no residual liquid phase. However, low Tmax parameters shows lower conjugate proportion (61%), which results in poor mechanical properties, hinders further development and application. Therefore, the low temperature single-step melting process with longer holding time had been developed, which increased the melting region and promoted the diffusion of atoms. It shows the conjugate proportion increased to 73.1% and trap field strength increased to 0.45KG
The optimal single-step process is used to fabricate the a-b plane joint technique (including (100)/(100)&(110)/(100) orientation) . The symmetry single cone shape and the asymmetry single-like cone shape morphology can be observed, the trapped field strength can reach to 1.08KG at 17mm x 17mm sample (77K,1T), almost the same as the self-prepared YBCO bulks (~ 1KG) by TSMT method with similar size. By 2D-XRD analysis (pole figure), single cone and single cone-like sample show good grain orientation result, it means that the single cone-like morphology affect by other reason. With micro-structure analysis, some Y211 lack region can be observed in the vicinity of joint boundary, and this area is considered related to the flow of liquid phase and push trap effect. Y211/Y123 boundary is an effect pinning center, therefore, this Y211 lack region will not be able to provide effective pinning center and decreasing the trapped field result. When comparing the trapped field result and specific surface area of Y211 at different position, it is found the trap filed indeed affect by this Y211 lack region.
Also the mechanical property of joint samples can be enhanced from 12.8Mpa to 72.7Mpa by carbon fiber coating. The sample of c-axis joint and a-b plane joint can trap 2.1KG and 5KG respectively at 45K, 3T and did not rupture.

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