The effect of Ho to the flux pinning and microstructure of powder melting process Y(Ho)BCO samples

Abstract

The structural and electrical properties of Bi2Sr2Ca1-xPrxCu2O8+delta have been investigated as a function of x. Powder-x-ray-diffraction patterns indicate that this system forms a continuous solid solution. It is found that phase separation exists in this system. Two phases with different modulated periods appear as the Pr doping changes. At low doping levels, the short-period phase dominates, while at high doping levels the long-period phase dominates. The short-period phase and the long-period phase are thought to correspond to the poor-Pr- and rich-Pr-concentration phases, respectively. T(c) was found to increase slightly for x less-than-or-equal-to 0.1, decrease linearly for 0.1 less-than-or-equal-to x less-than-or-equal-to 0.4, then to be depressed rapidly for 0.4 less-than-or-equal-to x less-than-or-equal-to 0.5, and finally to disappear at x = 0.6. The valence of Pr was inferred to be close to +3 from the measurement of the oxygen content and the comparison with other rare-earth-doped Bi-2212 systems. The variation of T(c) was explained in terms of hole filling and phase separation.