The present work describes the effect of mechanical milling with a vibration ball mill before and after the calcining on the superconductivity, The experimental results showed that the first-step milling before calcining had a greater effect on the critical temperature of the final sintered pellet than the second-step milling after it. Moreover, it was shown that there was a proper range of the first-step milling time to obtain high superconductivity, i.e., too long first-milling caused the reduction of the critical temperature of the sintered product. The same tendency was confirmed by the measurement of susceptibility of the calcined powder. The reason for the degradation of superconductivity by the prolonged milling was ascribed to the inhomogeneity caused by the strong agglomeration of the component particles which was confirmed by the size analysis, observation with a scanning electron microscope and measurement of bulk density of the milled powder. Furthermore, the X-ray diffraction analysis showed that the peak intensity of the superconducting phase of the milled powder decreased gradually with the time of second-step milling after the calcining, though the second-step milling time did not affect the critical temperature of the final product within the range of milling time in the present work.
