SUPERCONDUCTING PROPERTY AND STRUCTURE STUDIES OF YBA2CU3O7-AG2O COMPOSITES

We have studied the superconducting property and the structure of YBa2Cu3O7 added with Ag2O, with the weight ratios of YBa2Cu3O7 to Ag equal to 4, 6, 8, and 10. Resistance and magnetization measurements show that the normal-state transport behavior and the superconducting transition temperature, Tc, are insensitive to the amount of Ag added. The normal-state resistance decreases linearly with temperature, reaching a large value of ≅ 3 for the ratio R(300 K)/R(100 K). This value is evidently larger than that (≤ 2.5) generally observed in polycrystalline YBa2Cu3O7, and is ascribed to the improved grain growth behavior resulting from Ag addition. X-ray diffraction and scanning electron microscopy studies have also been performed. X-ray diffraction study indicates the Ag peaks appear as a separate phase. Scanning electron microscopy study reveals large YBa2Cu3O7 grains (≅20–60 µm). Finally, we point out that the microstructures of the samples depend much on the subtle preparation conditions. © 1990 The Japan Society of Applied Physics.