New model to tune the dielectric properties of dense and half-dense sintered polycrystalline cu-doped Ni–Zn ferrite

Abstract

Sintered polycrystalline Cu-doped Ni–Zn ferrite specimens have been successfully prepared by a conventional ceramic method using different pressure-temperature-time cycles. The studied samples, with an average grain size of 5–25 μm and a porosity less than 0.20, exhibited a high effective complex permittivity-real part (εeff') and a minimum dielectric loss above 1 GHz.εeff' was successfully calculated using the Bruggeman-Landauer equation for the lowest angular frequencies and the Jayasundere-Smith equation for the highest one. To accurately predict the values of εeff', both equations must be improved considering the Zheng approach. The need to change the model highlights the change in the polarization mechanism that occurs at high angular frequencies.The two proposed modified equations allow predicting the εeff' for a dense and half-dense ferrite from its microstructure (porosity) and its constituent permittivities (grain and air).