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In the present paper, the gallium modified lead zirconate titanate ceramics with Zr/Ti = 48/52 (near the morphotropic phase boundary, MPB), having a chemical formula Pb0.98Ga0.02(Zr0.48Ti0.52)0.995O3, was synthesized by a mixed-oxide reaction method and sintered. Analysis of phase formation confirmed the co-existence of two phases (tetragonal and monoclinic symmetry) in the system. Microstructural study by scanning electron microscope showed a non-uniform distribution of large grains over the sample surface and presence of a small amount of micro-size pores. Modulus and impedance studies were carried out at various frequencies (1 kHz–1 MHz) and temperatures (300–350 °C) and showed the contributions of grains in capacitive and resistive properties of the material. The resistance and capacitance of the complex impedance plots are contributed by grains as observed from the Nyquist plots. The experimental data obtained from the Nyquist plot were implemented in an equivalent electrical circuit (RQC). The value of grain resistance and capacitance were obtained using fitting steps with precision at all temperatures. It is assumed that increase of dielectric constant at higher temperatures is due to the substitution of Ga+ ions at the Pb-site.

Novel three phase composites were prepared by embedding nanographite (GNP) and lead zircon ate titanate (Pb(ZrTi)O3; PZT) into the polyvinyl alcohol (PVA) matrix via solution casting technique. The structural analysis was carried out by using X-ray diffraction technique, which indicated the tetragonal structure of Pb(ZrTi)O3 (PZT). The frequency dependences of dielectric, electrical and ferroelectric properties of the PVA-PZT-GNP composites on different volume fractions of GNP were investigated. The percolation theory was used to progress the dielectric and electrical performance of PVA-PZT-GNP composite. It was observed that the PVA-PZT-GNP composite showed insulator-conductor transition with percolation threshold of 5 vol% of nanographite. The dielectric permittivity of PVA-PZT-GNP composite was achieved as high as ≈117 at 100 Hz at percolation threshold, which was about 17 and 5 times higher than that of pure PVA and PVA-PZT composite, respectively. The ferroelectric hysteresis loop investigation indicated that the three phase composites exhibited much higher electric polarization than that of two phase PVA-PZT composite systems. [ABSTRACT FROM AUTHOR]