REACTION SINTERING PROCESS IN GRANULAR COMPOSITES: APPLICATION TO A SUPERCONDUCTOR/FERRITE SYSTEM

摘要

Granular superconductor-ferrite (S/F) composites have been fabricated using various sintering conditions (volume fraction PHI0 of ferrite, volume fraction SIGMA0 of superconductor, sintering temperature Tsint, sintering time tsint). The superconducting S phase is the well-known Bi(Pb)-2223 phase (Tc=110 K). The ferrite (F) is NiFe2O4. The reaction sintering process is experimentally described by determining the volume fractions of residual S and F phases from XRD experiments. Magnetic measurements are used to analyze the degradation process in both residual ferrite and superconducting phases. Nonlinear evolutions of the SIGMA and PHI residual volume fractions as a function of initial compositions are observed. To interpret these results, authors propose to express the chemical kinetics using two elemental reactions such as: F+n. S yields P and S+S yields P'. Using various types of kinetics parameters, the solid state reaction in each composite can be modeled as a function of the initial SIGMA0 and PHI0 volume fractions. 32 refs.