Microstructure and AC-Susceptibility of (Y,Ca)Ba2Cu4O8 Superconductors Prepared at Low (3 atm) and High (400 atm) Oxygen Pressure
Superconductive (Y1−xCax)Ba2Cu4O8 (x=0.0 and 0.05) ceramics were successfully prepared by firing for 160 h at 850 °C and at an oxygen partial pressure of 3 atm without using any catalysts. These samples were characterized by x-ray powder diffraction, scanning electron microscope (SEM) and electrical resistivity and ac magnetic susceptibility measurements. The x-ray powder diffraction pattern changed little after post-annealing for 6 h at 1070 °C and at oxygen partial pressure of 400 atm. The grains in the sample prepared at P(O2)=3 atm were small and poorly sintered, while grains in the post-annealed sample at P(O2)=400 atm were large and well sintered to be rectangular shaped. The temperature dependence of both the real and imaginary components, x ′, and x ″, of the ac susceptibility was measured. The width of x ′ at the superconducting transition temperature for the post-annealed samples was narrower than that for as-sintered samples.
KeywordsElectrical Resistivity Oxygen Partial Pressure Superconducting Transition Temperature Imaginary Component Cold Isostatic Pressing
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