Sintering effects in superconducting Fe-based YBCO composites: simulation of electrical resistances at low temperature

Various low temperature electrical behaviours observed in sintered Fe/YBa2Cu3O7−δ superconducting composites are briefly reported. The influence of sintering temperature and Fe composition on the superconducting electrical properties is discussed in terms of the chemical reactivity of Fe/YBa2Cu3O7−δ. To interpret such resistance variations, a semi-empirical approach is used: in the model the existence of superconducting paths in the composite depends on the fraction of Fe; the sintering processes can be described from the interface resistances which vary at low temperature. A unique resistance ratio characteristic of grain surface and grain core evolutions can be defined from the model to interpret the macroscopic electrical observations. The good agreement between the calculated and experimental R(T) variations allows characterization of the interfaces which develop during the sintering process.