High-K tungsten-mullite composite for electronic industrial application: synthesis and study of its microstructure, phase behavior and electrical properties

Highly crystallized mullite synthesis with different concentration of tungsten ions has been achieved by sol–gel technique and the effect of tungsten ion doping on mullite was examined at 1,100 and 1,400 °C. Characterizations were done by DTA/TGA, XRD, FTIR, LCR and FESEM instruments at the room temperature. Mullite formation was found to depend on the concentration of the doping ion up to a certain extent. With the addition of tungsten ion, the mullite formation temperature was decreased. The result showed a decrease in mullite phase at higher concentrations of doping ion with respect to undoped mullite. Oxide phases continued to increase with increasing doping concentration, which is mainly responsible for the increment in dielectric value. Dielectric value of the doped mullite was found to decrease with the increase in frequency for all the samples and saturates at higher frequency, which is normal behavior for dielectric ceramics. A.C. conductivity increased with frequency by following Jonscher’s power law. The composite showed maximum dielectric constant of 124.02 sintered at 1,400 °C for 0.05 M at 20 Hz frequency. Highly crystalline mullite whiskers of average dimension 3 μm were obtained at 0.02 tungsten concentration sintered at 1,400 °C. Due to the good dielectric response, comparatively low loss and appropriate nature of the doped mullite it can be used as ceramic capacitors, packaging material for integrated high speed devices. Also, it’s electrical and thermal suitability may prove to be significant as the insulator material of the spark plug.