Polycrystalline samples of manganese and iron substituted lead zirconium titanate (PZT) with general formula Pb(Zr0.65？xAxTi0.35)O3 (A = Mn3+ and Fe3+) ceramics have been synthesized by high temperature solid state reaction technique. X-ray diffraction (XRD) patterns were recorded at room temperature to study the crystal structure. All the patterns could be refined by employing the Rietveld method to R3c space group with rhombohedral symmetry. Microstructural properties of the materials were analyzed by scanning electron microscope (SEM), and compositional analysis was carried out by energy dispersive spectrum (EDS) measurements. All the materials exhibit ferroelectric to paraelectric transition. The variation of dielectric constant and loss tangent with temperature and frequency is investigated. The decrease of activation energy and increases of AC conductivity with the Fe3+ or Mn3+ ion concentration have been observed. The AC conductivity has been analyzed by the power law. The frequency exponent with the function of temperature has been analyzed by assuming that the AC conduction mechanism is the correlated barrier hopping (CBH) model. The conduction in the present sample is found to be of bipolaron type for Mn3+ ion-doped sample. However, the conduction mechanism could not be explained by CBH model for Fe3+ ion-doped sample. 1. Introduction Pb-based ceramic oxides have been widely studied due to their excellent ferroelectric, dielectric, and piezoelectric properties [1–3]. In particular, PbTiO3-based solid solutions have dominated for decades the technological field responsible for the development of piezoelectric materials [4]. Lead zirconium titanate (PZT) belongs to the perovskite structural family of a general formula ABO3 in which A site is occupied by Pb2+ ions and B site by Zr4+ or/and Ti4+ ions [1–3]. Fluctuation of the oxidation state of Mn3+/Fe3+ ions results in the formation of oxygen ion vacancies to reserve the local electrical neutrality and causes thermally activated conduction. PZT is a solid solution of ferroelectric PbTiO3 (PT with °C) and antiferroelectric PbZrO3 (PZ with °C) with different Zr/Ti ratios and has two ferroelectric phases: a tetragonal phase in the titanium rich side of the binary system and a rhombohedral phase in the zirconium rich side [5, 6]. The boundary line between these two phases is called morphotropic phase boundary (MPB) at which dielectric and conductive properties rise to a great extent [7]. A wide variety of complex compounds (other than the above) can be prepared by substituting suitable elements at
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