## Microstructural, structural and electrical properties of bilayered BaZr0.05Ti0.95O3/Ba0.75Sr0.25TiO3 ceramics

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Abstract
08-099 Eduardo Antonelli Antonelli, E.(Universidade Federal de São Paulo); Serrano, A.G.(Universidade Federal de São Paulo); Boschilia Junior, R.(Universidade federal de São Paulo); Boaventura, A.L.(UNIFESP); One of the main subjects in electroceramics studies is how to improve or tune one specific electrical property for a defined application. It has been demonstrated that compositional and/or microstructural engineering is an efficient way to optimize the electrical properties of this class of materials. Alternatively, the preparation of ceramic composites for this purpose has been recently proposed. This work reports the preparation of bilayered ceramics of ${\mathrm{BaZr}}_{0.05}{\mathrm{Ti}}_{0.95}{\mathrm{O}}_{3}$ and ${\mathrm{Ba}}_{0.75}{\mathrm{Sr}}_{0.25}{\mathrm{TiO}}_{3}$. The studied materials were prepared through the conventional ceramic method. After homogenization for 12 h, the powders were calcined at 1200${}^{\mathrm{o}}\mathrm{C}$ for 2 h. The powders were then ball-milled for 12 h into fine powders. The bilayers were prepared by the powder-stacking method and uniaxial pressing. The powders were compacted into disk-shaped samples (6 mm in diameter) with layers of each material. All the samples were sintered in an indirect microwave furnace at 1320${}^{\mathrm{o}}\mathrm{C}$ for 2 h. The final density of each sintered specimen was determined by the Archimedes method, showing values of the BaTi${\mathrm{O}}_{3}$’s theoretical density of above 95% in all cases. Both the modified phase and microstructural developments were followed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Thermal shrinkage was measured using a dilatometer. Electrical measurements were carried out from room temperature to about 450${}^{\mathrm{o}}\mathrm{C}$. Crack-free and high-density composites were obtained despite the different contraction coefficients of the layers during the sintering. The electric properties of the bilayers are evaluated and discussed in terms of the individual capacitance and resistivity of each composition. In particular, one diffusion layer (~20 µm) that has an important effect on the material’s overall behaviour was observed.
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