The Alternative Expression of Lichtenecker's Logarithmic Mixture Formula and Its Application to the Broadband Dielectric Spectroscopy of BaTiO3-Ni0.5Zn0.5Fe2O4 Composites

The experimental data of xBaTiO(3) - (1-x)Ni0.5Zn0.5Fe2O4 (BT-NZF) composites with volume ratios x = 0.466, 0.567 and 0.67 are analysed using Lichtenecker's logarithmic mixture formula and its newly suggested alternative expression. Application of Lichtenecker's logarithmic mixture formula is limited by the influence of conductivity to the response of the effective permittivity. Therefore an alternative expression, that allows constituents behaviour of the composite to be described separately by changing frequency with a fixed volume fraction, is suggested. For the present purpose, it is assumed that the real part of each component has no dispersion and is equal to the static permittivity of pure material, while the imaginary part is dependent on the presence of conductivity. By applying the alternative expression for each of the composition over a broad frequency and temperature ranges separately, the parameters obtained are analysed and compared. The composite with the volume ratio of x = 0.466 exhibits moderate deviation from the other two compositions, presumably caused by the difference in their homogeneities, defectivities, grain-size effects and/or microstructural changes during the preparation and sintering process.