IMF2017

Ferroelectric materials are fundamental to capacitors industry due to their dielectric properties. However, their excellent dielectric properties are closely related to structural phase transitions and their spontaneous polarization. Accordingly, ferroelectric capacitors present a large variation in capacitance with temperature, high dielectric loss near the Curie temperature, fatigue and aging when submitted at an alternating electric field. Recently, the cubic perovskite CaCu₃Ti₄O₁₂ (CCTO) has drawn a lot of attention due to their giant dielectric constant (GDC). There are some hypotheses to explain the origin of the GDC in CCTO that, in general, are based on intrinsic or extrinsic factors. In the present work, the CCTO pure and doped with Mg²⁺ was prepared by the conventional ceramic method. The results here presented and discussed refer to the trend of Mg²⁺ occupation on the CCTO structure and their influence on the dielectric and interfacial properties. The pure and doped ceramic were sintered at 1050^oC for 3, 6 and 12 hours in a furnace. The phase and microstructure developments were followed by X-ray diffraction (XRD) using a Rigaku Ultima IV diffractometer (CuK_α, λ = 1.5406 Å) and scanning electron microscopy (FEI), respectively. Electrical measurements were carried out with a Solartron SI 1260 impedance/gain-phase analyzer over a wide temperature range from 25 to 200 ^oC. In particular, Mg²⁺ was seen to inhibit the materials’ grain growth process, besides promoting a decreasing of the GDC of CCTO. This decreasing on permittivity was related to the resistivity for grains and grains boundaries in doped-CCTO.