Liquid Phase Diffusion Bonding of High Temperature Ceramic Superconductivity to Metals

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Diffusion bond-ability of Y-Ba-Cu-O system high Tc superconductor using the mixture of silver oxide and YBCO powder as interlayr materials has been investigated by SEM/EDX analysis, differential thermal analysis, X-ray diffraction tests and examination on superconducting behavior of the joints. The joint strength was measured by shear fracture test using jigs, and the fracture pass was also observed by SEM/EDX.Differential thermal analysis results showed that silver oxide added to the superconductor decomposed at about 350C.X-ray diffraction test results in the vicinity of the joints suggested that the silver oxide supplies oxygen to the joint area and contributes to maintain the superconductivity of the joint. However, X-ray diffraction results showed that the thickness of the destroyed superconductive layr at the joint area was less than 0.3 mm from the bonded interface, and the superconductivity was impaired a little. On the contrary, the use of mixed powder of YBCO and silver oxide as interlayrs improved the bond-ability without the decrease of superconductivity at the joint area. In this bonding method, it is considered that decomposition and diffusion of the silver oxide into the base material assists the sintering of YBCO powder in the interlayr during the bonding thermal cycle.These results demonstrate the possibility of diffusion bonding of high Tc ceramic superconductor without impairing the superconductivity by using the mixed powder of silver oxide and YBCO powder.