Rietveld analysis, dielectric and impedance behaviour of Mn3+/Fe3+ ion modified Pb(Zr0.65Ti0.35)O3 perovskite

The polycrystalline samples of Pb(Zr0.65-xAxTi0.35)O3 (A = Mn/Fe), (x = 0.00, 0.05) (PZM/FT) were synthesized by conventional solid-state reaction technique. X-ray diffraction (XRD) pattern was recorded at room temperature and the samples were found in single phase form. All the observed peaks could be indexed to R3c space group with rhombohedral symmetry. XRD pattern has been analysed by employing Rietveld method with the help of FullProf Program. The lattice parameters and unit cell volumes decrease from Mn3+ to Fe3+ ion concentrations. The bond lengths and angles have been calculated by using Powder Cell Programme.Microstructural analysis of the surface of the ceramic compound by scanning electron microscopy (SEM) exhibits that there is a significant change in grain size on introduction of Mn3+ and Fe3+ ions at the Zr-site of the compound. It is observed that both the substitutions (Mn3+ and Fe3+) at Zr site induce an increase in dielectric constant and a shift in Curie temperature (Tc). From a.c. conductivity analysis, we have estimated the activation energy for both ferroelectric and paraelectric regions. Both the modified samples are obeying Jonscher power law. From Nyquist plots, the activation energy of grain resistance, relaxation time and bulk conductivity are compared. The grain resistance of the material decreases with rise in temperature which indicates a semiconducting behaviour of the material. (author)