Structural, Dielectric, and Impedance Properties of Sintered Al6Si2O13 Composite for Electronic Applications

Mullite (Al6Si2O13), an aluminosilicate with remarkable thermal and dielectric properties, is a promising material for advanced electronic applications. This study focuses on a sintered mullite composite and examines its structural, morphological, dielectric, and electrical properties. X-ray diffraction and scanning electron microscopy analyses confirm a well-defined crystalline structure and a homogeneous microstructure. Impedance spectroscopy measurements reveal a high relative permittivity at low frequencies, dominated by interfacial and jump polarization mechanisms. Electrical conductivity follows Jonscher’s double-power law, reflecting mixed ionic and electronic conduction due to contributions from grains and grain boundaries. Analysis of the Nyquist diagrams shows a marked decrease in resistances with increasing temperature: The grain resistance decreases from 21.87 MΩ to 4.85 MΩ, while that of the grain boundaries decreases from 89.44 MΩ to 5.94 MΩ between 450 °C and 900 °C. In addition, the relative permittivity increases sharply with temperature, from 25 × 103 to 350 × 103 at 1 kHz and from 200 to 1 × 103 at 1 MHz over the same temperature range, highlighting the dominant influence of temperature and low frequencies on polarization mechanisms. These results confirm the strong potential of sintered mullite for electronic applications. The activation energy of the grain and grain boundary were determined to be Ea,g = 0.18 eV and Ea,bg = 0.22 eV, respectively.