The improved performance of bulk MgB2 material with added nanometer-sized MgB4 particles is presented. Bulk polycrystalline MgB2 samples with varying amount of MgB4 x (x = 0, 1, 2, 3, 4, 5, and 10 wt%) are fabricated by solid-state sintering at 775 °C for 3 h in pure argon gas. Microstructural studies indicate formation of nanometer-sized grains when MgB4 is added. Density of nano-grains is inversely proportional to the MgB4 content. The MgB2 sample with 1 wt% of MgB4 shows the best performance, with its self-field critical current density reaching 385 and 315 kAcm−2 at 15 and 20 K, respectively. Flux pinning diagrams reveal the domination of grain boundary pinning mechanism.
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