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MgB 2 superconducting wires and bulks with nano-La 2 O 3 addition have been studied. A series of MgB 2 superconducting bulk samples with nano-La 2 O 3 addition levels of 0, 5, 7, 18wt% were prepared. AC resistivity data showed slight increases of Bc 2 and unchanged B irr for the bulk samples with doping levels lower than 7 wt% and decreased critical fields for the heavily doped (18 wt%) bulk. X-ray diffraction (XRD) showed the presence of LaB 6 in the nano-La 2 O 3 doped MgB 2 bulk samples and decreased MgB 2 grain size in nano-La 2 O 3 doped bulks. Monocore powder-in-tube (PIT) MgB 2 wires without and with 5 wt% nano-La 2 O 3 addition (P-05) were prepared for transport property measurement. 2mol%C-doped Specialty Materials Inc. (SMI) boron powder was used for wire P-05 and previously prepared control wires (control wires were made without the addition of nano-La 2 O 3 powder, W-00 and P2). Low field magnetic properties were obtained from magnetization loop (M-H), transport critical current density ( J c ) was measured at 4.2 K for the nano-La 2 O 3 doped PIT wire (P-05) and the control samples (P2 and W-00). The transport critical current density J c (B) of P-05 at 4.2 K and 8 T (6.0 ×10 4 A/cm 2 ) was twice that of the control wire. The critical magnetic fields ( Bc 2 and B irr ) of P-05 and the control sample P2 were compared. The critical fields of P-05 were slightly less than those of P2. Kramer-Dew-Hughes plots indicated a change from surface pinning to a mixture of volume pinning and surface pinning. It is shown that enhancement of P-05's transport properties is due to additional flux pinning by the fine-size rare-earth borides rather than enhanced Bc 2 or B irr .

Research into in-situ MgB 2 strand has been focused on improvements in J C through reduction of porosity. Both of cold-high-pressure-densification (CHPD) and advanced-internal-magnesium-infiltration (AIMI) techniques can effectively remove the voids in in-situ MgB 2 strands. This study shows the nature of the reduced porosity for in-situ MgB 2 strands lies on increases in transverse grain connectivity as well as longitudinal connectivity. The CHPD method bi-axially applying 1.0 GPa and 1.5 GPa yielded 4.2 K J CM∥ s of 9.6 × 10 4 A/cm 2 and 8.5 × 10 4 A/cm 2 at 5 T, respectively, with compared with 6.0 × 10 4 A/cm 2 for typical powder-in-tube (PIT) in-situ strand. Moreover, AIMI-processed monofilamentary MgB 2 strand obtained even higher J C s and transverse grain connectivity than the CHPD strands.