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Keywords:

  • complex impedance spectroscopy;
  • ferroelectric perovskites;
  • negative temperature coefficient of resistance;
  • polycrystalline composites, X-ray diffraction

Abstract

Polycrystalline composites of (1−x) (Ba0.7Sr0.3TiO3)–x(Ni0.5Zn0.5Fe2O4) (x = 0.00, 0.45, 1.00) were prepared by a modified wet chemical method followed by a high-temperature sintering process. X-ray diffraction (XRD) studies at room temperature confirmed the formation of perovskite-spinel structure. Scanning electron micrographs suggest polycrystalline microstructure with grains of unequal size distributed throughout the samples. Dielectric studies of the composites reveal that the effect of ferrite in the composites is to shift the ferroelectric–non-ferroelectric phase transition to the higher temperature side with a broadened Curie temperature transition. Complex impedance spectroscopy analysis indicated negative temperature coefficient of resistance behavior, identical to semiconductors. The conduction at low temperature is due to impurities, whereas at higher temperature it is due to polaron hopping.