Preparation and dielectric properties of Ag-BaTiO3 composite ceramics

Reference	Presenter	Authors (Institution)	Abstract
08-053	Cristina Elena Ciomaga	Ciomaga, C.(Al. I. Cuza University of Iasi); Curecheriu, L.(Alexandru Ioan Cuza University); Turcan, I.(Alexandru Ioan Cuza University); Lukacs, A.(Alexandru Ioan Cuza University); Stoian, G.(National Institute of Research and Development for Technical Physics); Lupu, N.(National Institute of Research and Development for Technical Physics); MITOSERIU, L.(Al. I. Cuza University of Iasi); Padurariu, L.(Al. I. Cuza University of Iasi);	The aim of the present work is to optimize the sintering parameters in ${\mathrm{BaTiO}}_3$ – based composites with a small amount of Ag filler, far below the percolation range (5% vol. Ag) in an attempt to increase permittivity by a synergy effect of the high density, metallic particles presence and ceramic grain size in the range of ?1µm, where ${\mathrm{BaTiO}}_3$ has a well-known maximum of its permittivity. Ag-${\mathrm{BaTiO}}_3$ composite ceramics were obtained by solid state method sintered for 2 h in air atmosphere at different temperatures: ${1000}^{°}{\mathrm{C}}^{}$- ${1300}^{°}\mathrm{C}$. The structural analysis revealed that for both pure ${\mathrm{BaTiO}}_3$ ceramics and in the Ag-${\mathrm{BaTiO}}_3$ ceramic composites, the pseudocubic perovskite phase characteristic to the starting ${\mathrm{BaTiO}}_3$ fine powders transforms into an orthorhombic Amm2 one after sintering. In all the composites, only the specific peaks of the parent phases ${\mathrm{BaTiO}}_3$ and cubic Fm3m silver were observed, without the presence of secondary phases, thus confirming the formation of di-phase composites in the nominal amount of 5% Ag. The SEM micrographs indicate an increasing grain size when increasing the sintering temperature, from ?350nm for the ceramic sintered at the lowest temperature of $1000°$C/2h, to ?2800nm for the one sintered at $1300°$C/2h. Finite Element Method was employed to estimate the role of Ag addition on the electrical properties of ${\mathrm{BaTiO}}_3$ - based composites and it confirmed that the major impact of the Ag addition is on the grain size of BT which tends to be ~1 µm, thus explaining the large values of the effective permittivity. The dielectric properties vs. temperature and frequency have been investigated and discussed. Acknowledgements: This work was supported by the UEFISCDI Romanian PN-III-P4-ID-PCE-2016-0817 grant.
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