X-ray absorption spectroscopic study of a hot pressed MgB2

X-ray near edge absorption spectra (XANES) of boron and oxygen K edge of a hot-pressed MgB2 (HP2) sample were measured by using synchrotron radiation. The HP2 was produced by annealing a commercial powder of MgB2 in ambient air under a hydrostatic pressure of 2.0 GPa at 900 °C. No substantial change of the electronic structure in HP2 was observed as indicated in the B K-edge XANES. This sample maintains high superconductivity and enhances the critical current density. The XANES and the XRD combined indicate that both MgO and B2O3 in HP2 increase and more B2O3 than MgO was produced during the hot-press process. The better connection of the grain in HP2 can be the major cause to increase its critical current density. However, the impurity may also increase the flux pinning and therefore increases the current density.