Initial permeability of percolative PbTiO3/NiFe2O4 composite ceramics by a sol–gel in situ process

Abstract

Percolative ferroelectric/ferrimagnetic PbTiO₃ (PTO)/NiFe₂O₄ (NFO) composite ceramics are prepared in situ by a sol–gel process. Results show that the NFO particles are well surrounded naturally by only a thin PTO layer, which leads to much higher percolation threshold (0.85) than the universal one (about 0.2) and thus the percolative PTO/NFO ceramics exhibit not only super high dielectric constant but also high initial permeability. In the percolative composite ceramics, both the changeable grain size and the variable impurities doped influence simultaneously the initial permeability of the NFO phase in the composite. Related with the continuous change in both grain size of the NFO phase and impurities doped into the NFO phase, the new behaviors of initial permeability appear in the composite ceramics, which is consistent with the new revised BH and MG models deduced for the composite ceramics in which the initial permeability of NFO is believably dependent on the chemical composition of the composite. Also, the new phenomenon occurs most probably in a general composite system in which the interaction between the two constituent phases occur normally, being consistent with the new deduced BH and MG expressions.