Abstract
Electrical properties of composite consisted of epoxy-glue and powdered bismuth manganite Bi12MnO20–BiMn2O5 ceramics were studied. Samples contained 66 wt% of bismuth manganite. Secondary electron images and backscattered electron images were collected for the epoxy-glue and the epoxy-glue/bismuth manganite samples. Microanalysis shown that majority of bismuth manganite powder was homogenously distributed in epoxy-glue matrix. Lack of changes in crystallographic structure, in 300–450 K range, was deduced from the X-ray diffraction patterns. The electric impedance was measured at radio-frequencies. It was analysed using electric permittivity ɛ*( T, f ) and modulus M″(T, f ) representation. Epoxy-glue/bismuth manganite composite exhibited, at room temperature, conductivity, σ( f ) = 10−5 to 10−7 S m−1, permittivity, ɛ′≈10, losses, tan δ = 0.2–0.8 and dispersion markedly lower than bismuth manganite ceramics. Electric relaxation was induced in epoxy-glue/bismuth manganite composite samples. The Vogel–Fulcher–Tammann equation was fitted to relaxation times temperature dependence, obtained from M″(T, f ). The estimated values of Vogel–Fulcher equation parameters were frequency f0 = 2.2 × 108 Hz, energy UT = 1050 K and glass transition temperature Tg = 282 K. The relaxation times were attributed to strains, which would occur at interfacial layers between the bismuth manganite grain and the polymer matrix.
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