Study on the carbon doping of sugar added MgB2 superconductors prepared by low temperature sintering
With sugar as an addition, the active carbon released from sugar can lead to the effective carbon doping in MgB2 superconductors only under the condition of high temperature sintering. However, this kind of carbon doping cannot occur at low temperature sintering condition. The reason is that the carbon released from the decomposition reaction of the sugar added in MgB2 has very low chemical activity during low temperature sintering process, which is similar with the results of elemental carbon or graphite doping directly. Thus, only the sintering temperature reaches a certain temperature or more (generally greater than 700°C), the carbon can possess sufficiently high chemical activity and go into the lattice of MgB2 to replace the B. In the condition of low temperature, it is difficult to form an effective carbon-doped.