Influence of Bi, Se and Te additions on the formation temperature ofMgB2

Abstract

The formation of the MgB2 superconducting compound from a mixture of Mg and amorphous B powderswith various low melting point metals (Bi, Se and Te) was studied in situ bymeans of high-energy (synchrotron) x-ray diffraction in wires with a compositeCu/Nb sheath. In comparison with an undoped sample, it was found that theaddition of Bi results in a clear lowering of the formation temperature ofMgB2, whereas Se and Te have no significant influence.Tc is slightly higher in the Bi-doped sample than in the others but thejc in this case is lowerthan in the pure MgB2 sample, probably due to the presence of remainingMg3Bi2 particles that formed as an intermediate compound during reaction. Likewise,in the Se-and Te-doped samples, MgSe and MgTe respectively form below450 °C. Whereasjc is also depressed in the Se-doped sample, the MgTe particles do not appear to affect theperformance of the Te-doped wire.