supported in part by the Department of Physics,Peking University;in part by the Center for Research and Development of Superconductivity in China under contract No.BKBRSF-G19990646-02
Project supported by Grant R850009 from Academia Sinica
Ⅰ. EXPERIMENTAL Magnesium tetraborate, MgB4O7·9H2O was synthesized from grade A. R. reagents. Its composition is (wt%) MgO 11.83, B2O3 40.76, H2O 47.43, B2O3/MgO (mole ratio) 1.995. It was identified as hungtsa...