Effect of sintering temperature under high pressure on the superconductivity of MgB2

We report on the effect of sintering temperature on the superconductivity of MgB2 pellets prepared under a high pressure of 3 GPa. The superconducting properties of the nonheated MgB2 were poor. However, as the sintering temperature increased, the superconducting properties were vastly enhanced, which was demonstrated by the narrow transition width for the resistivity and the low-field magnetization. The observed surface morphology using scanning electron microscopy showed that these changes were closely related to changes in the microscopic level such as the connectivity of the grains. (C) 2001 American Institute of Physics.