Superconducting properties of PIT-processedMgB2 tapesusing Mg(BH4)2 precursor

Abstract

We have fabricated MgB2 superconducting tapes with a powder-in-tube (PIT) technique usingMg(BH4)2 precursor. Heattreatment decomposes Mg(BH4)2 and subsequently forms MgB2 as nearly single phase. Although the tapes carry supercurrent at 4.2 K and 0 T, the transport criticalcurrent (Ic) values of the tapes decrease down to 0 A by applying a magnetic field as small as 1 T. This is dueto the weak grain coupling brought about by the large reduction in volume at the formation ofMgB2 fromMg(BH4)2. On the other hand, the use of the intermediates obtained by the calcination ofMg(BH4)2 powder successfully improves the critical current density (Jc) property close to the level of tapes using conventionalMg + B powders, owing to the suppression of the reduction. The insufficient purity of the starting precursorand the high sensitivity of calcined powder to oxygen and moisture prevent further improvement in theJc property.