Elastic and Dielectric Properties of Active Ag/BaTiO3 Composites
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2017, Society for Experimental Mechanics. This study examines the elastic and dielectric properties of active composites consisting of barium titanate (BaTiO3) and silver (Ag) constituents using experimental and numerical approaches. The elastic constants including Youngs modulus, shear modulus and Poissons ratio were measured by resonant ultrasound spectroscopy (RUS), a nondestructive dynamic technique, while a dielectric (impedance) spectroscopy was used to measure the relative permittivity and dielectric loss at different frequencies. The dielectric tests were also conducted at temperature ranges from 50 to 200C where the two phase transformations of barium titanate at around 0C and 120C were examined. The experimental results in this study were compared to data available in the literature. In addition to the experimental work, a numerical method is also considered in order to study the effects of blending silver into barium titanate on the effective elastic and dielectric properties of the composite and the local field fluctuations. For this purpose, two micromechanics models describing the detailed composite microstructures were constructed. The first model is based on two dimensional (2D) images of realistic microstructures obtained by the scanning electronic microscopy (SEM), while the second model is based on randomly generated three-dimensional (3D) microstructures with spherical particles. The effects of loading direction, porosity, particle shape and dispersion were examined using the micromechanics models. Numerical predictions of the effective elastic and dielectric constants were compared to the experiment results.
