A comparative electrical study of nano-crystalline mullite with low dielectric loss due to incorporation of tungsten and molybdenum ion: their uses in electronic industries

Because of the importance of ceramic materials, a large number of papers dealing with the fabrication, characterization, and the use of mullite in traditional and advanced ceramics and in oxide-based ceramic composites has been published in recent years. The wide use of mullite ceramics can be explained by its favorable high-temperature properties such as high thermal stability even in adverse oxidizing conditions, low thermal expansion and thermal conductivity, favorable thermal shock, and low creep resistances. Here crystallized mullite composites have been synthesized at 1100 °C via sol–gel technique in presence of tungsten and molybdenum ion, and their comparative studies have been examined. Crystalline phases have been identified by XRD and FTIR instruments. Morphology of the samples was investigated by FESEM. Electrical properties of the composites have been measured by LCR Meter at room temperature and their variation with increasing frequency and concentration of the doped metals has been investigated. The composite doped with tungsten ion exhibits maximum dielectric constant of 29.18 with dielectric loss of 0.076 and molybdenum ion exhibits maximum dielectric constant of 17.62 with dielectric loss of 0.038 at 0.05 M concentration at 2 MHz frequency. Experimental data shows a linear increase in A.C. conductivity with increasing concentration of metal doping ions. In spite of its importance as a high-temperature ceramic and composite material, mullite shows fairly convincing electrical conductivity at high temperature and high frequency. The dielectric constant and loss tangent of the composites are within the range of requirements for commercial use in electronics industries.