LAUSR

Abstract A series of MgB 2 samples doped with C, RE 2 O 3 oxides (RE = Ce, Nd), and C and RE 2 O 3 oxides was prepared by the hot isostatic pressing method at high pressure: 1 GPa under argon gas. Based on X-ray diffraction and magnetization measurements it was found that the RE 2 O 3 is not incorporated into MgB 2 . A secondary REB 4 phase is present after the synthesis. No decrease in the critical temperature ( T c ) is observed after the RE 2 O 3 doping. The T c of C and RE 2 O 3 doped MgB 2 is decreased by 3 K. The doping decreases the diamagnetic response in comparison to pure MgB 2 phase. The highest critical current density ( J c ) was 3.4 × 10 5 A/cm 2 at 4.2 K and 0.5 T for the bulk material, and the irreversibility field for the Nd 2 O 3 doped sample was located at high field at T  = 30 K. The results indicate that inside grains of pinning centers increase J c from 4.2 K to 25 K and decrease J c at 30 K. On the other hand, pinning centers between grains (precipitate) increase J c at 30 K and decrease J c from 4.2 K to 25 K in the middle and high magnetic fields. Our research shows that carbon-encapsulated boron creates a point pinning centers.