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

Abstract

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.

Structural, optical and dielectric properties of Cu1.5Mn1.5O4 spinel nanoparticles

“…Whereas, at high frequency, the losses are reduced and the dipoles contribute to the polarization because the dipole polarization can orient themselves with the electric eld, due to high conductivity. 97 Finally, these results indicate that the Cu 1.5 Mn 1.5 O 4 nanoparticle sample could be used in many technological applications, e.g., Li-ion batteries, fuel cells, microwaves, and lowtemperature cored ceramics (LTCC) technology applications.…”

Synthesis of nanocrystalline photoluminescent mullite using sacrificial cotton wool and filter paper templates

“…Doping with Mo and W introduced alumina and silica phases for cotton wool templated samples at both the sintering temperatures whereas in case of filter paper template only enhancement of mullitization occurred as a result of doping without any reflection of additional phases. Intermediate formation of aluminum molybdate (Al 2 (MoO 4 ) 3 ) and aluminum tungstate (AlWO 4 ) may be responsible for the segregation of alumina and silica phases and enhancement of mullitization . The influence of molybdenum on phase transformation of mullite is due to the formation and decomposition of aluminum molybdate resulting from the interaction of alumina and molybdena (MoO 3 ) phase which is governed from sodium molybdate doping.…”

Sol–gel synthesis of transition-metal ion conjugated alumina-rich mullite nanocomposites with potential mechanical, dielectric and photoluminescence properties

“…25,46 Generally loss in the mullite composites happens due to the migration of mobile cations and deformation losses from the network constructed by silica. 47 It was reported earlier from the Cole-Cole plot of dielectric permittivity that Debye-like relaxation is the most dominant relaxation type which can occur in mullite ceramics. 48 Thus, non-linear increase of tangent losses which was observed for all three transition-metal ions doped mullite composite (Fig.…”

“…At high frequency, higher conductivity resulting in exchange of electrons between two conducting grains becomes favourable, resulting a decrease in loss. 47 The ac conductivities of cobalt, nickel and copper ion doped mullite composites are shown in Fig. 11c, f and i respectively.…”