Influence of interfacial stresses on electrical properties of bismuth manganite – lead titanate – epoxy composite

Abstract This work compares the dielectric properties of two new materials. One was 0.88 bismuth manganite–0.12 lead titanate (noted BM–PT hereafter) ceramics composite obtained by standard high-temperature sintering. The second composite was obtained from powdered ceramics dispersed in epoxy glue (noted BM–PT–epoxy). The occurrence of four phases in the ceramics, using X-ray powder diffraction (XRD), was recognized: orthorhombic Pbam, cubic Pn 3 ‾ m, cubic Pm 3 ‾ m, and monoclinic P2/m phase. Pseudo-Voigt function fitting confirmed significant structural disorder in the BiMn2O5 crystal lattice. Analysis of broadband dielectric spectroscopy data confirmed the applicability of the small polaron model to explain detected relaxation processes. Involvement of oxygen vacancies in relaxation and their correspondence to ordered, uniform potential wells in crystal lattices was deduced. Electric conductivity relaxation times behavior proved the sensitivity of the ceramics’ electrical features to hydrostatic pressure. BM–PT–epoxy composite exhibited dielectric permittivity and losses two orders of magnitude lower than those of BM–PT ceramics that opened new prospects to application. One relaxation process in BM–PT–epoxy composite related to the ceramics fill contribution. Other induced relaxation, observed only in this composite, was attributed to interactions at interfaces between the introduced powdered ceramics and the epoxy glue matrix. We showed that stresses generated either by hydrostatic pressure or through the interfacial interaction of epoxy matrix led to the same results: relaxation times shortening.