Nucleation and growth of dense phase in compressed MgB2

We report nucleation and growth of dense MgB2 phase in two advanced methods for compacting MgB2 powder: hot isostatic pressing (HIP) and resistive sintering (RS). Both methods produce a compact with nearly theoretical mass density and high critical current density: up to 8.10(5) A/cm(2) at 20 K. A liquid phase is responsible for the propagation of dense MgB2. The additions of Mg and Ni are beneficial for rapid formation of dense compact. The process of compacting is further improved by introducing single crystal-dense MgB2 seeds.