Diffused phase transition, ionic conduction mechanisms and electric-field dependent ferroelectricity of Nb/Ce co-doped Pb(Zr0.52Ti0.48)O3 ceramics

Abstract

In this work, polycrystalline ceramics of the Pb(Zr0.52Ti0.48)0.95Nb0.05O3 + 0.2 wt% CeO2 (PZT-NC) compound were fabricated by the conventional solid-state reaction process from oxide precursors. Firstly, XRD analysis and SEM observation associated with EDS mapping were used for characterizing the phase structure, grain morphology and element composition of the specimens, respectively. And then, the temperature dependence of the dielectric properties were studied for the specimens in a wide frequency range of 1 kHz–1 MHz. The diffused phase transition behavior were comprehensively characterized in terms of the modified Curie-Weiss law involved in diffuseness and diffusivity. The dielectric loss mechanisms were explained by space charge conduction and domain wall relaxation. Further, the temperature dependent AC conductivity of the specimens were analyzed at a low frequency of 1 kHz. The electrical conduction mechanisms in three temperature regions: room temperature∼250 °C, 250∼400 °C, and 400∼500 °C, were associated with three different kinds of charge carriers. Finally, the polarization switching properties of the specimens were measured with the applied electric field of 30–50 kV/cm. The linear variation of coercive field, remanent polarization and maximum polarization with the electric-field amplitude demonstrated the field dependent ferroelectricity. As profited from the co-doping effect of Nb/Ce applied in the B-/A-site of the perovskite structure, the PZT-NC ceramics achieved many optimized electrical properties, including a high d33 (443 pC/N) and Tc (312 °C), a large g33 (35 × 10−3 Vm/N) and Pr (∼24 μC/cm2), as well as a low Ec (∼10 kV/cm), which make it possible for prospective applications in piezoelectric/ferroelectric devices.