Synthesis of Denser In Situ $\hbox {MgB}_{2}$ Bulks Using $\hbox {MgB}_{4}$ Precursor

We have synthesized bulks from a laboratory-made precursor that have higher packing factor (relative density) compared to conventional in situ bulks from boron. precursor with less MgO content can be obtained by decomposition of under low magnesium partial pressure. bulks fabricated by heating the mixed powders of Mg and showed improved packing factor 61%, high connectivity , and at 20 K under self-field. Both and are the highest among the literatures for samples synthesized from precursor. Our results suggest that the in situ reaction route is effective for densification of in situ , and much higher connectivity and can be reasonably expected by further optimization of the preparation of the precursor and reaction conditions.