Abrupt change of dielectric properties in mullite due to titanium and strontium incorporation by sol-gel method

Abstract

Highly crystallized mullite has been achieved at temperatures of 1100 ℃ and 1400 ℃ by sol-gel technique in presence of titanium and strontium ions of different concentrations: G0 = 0 M, G1 = 0.002 M, G2 = 0.01 M, G3 = 0.02 M, G4 = 0.1 M, G5 = 0.2 M and G6 = 0.5 M. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), LCR meter characterized the samples. Mullite formation was found to depend on the concentration of the ions. The dielectric properties (dielectric constant, loss tangent and AC conductivity) of the composites have been measured, and their variation with increasing frequency and concentration of the doped metals was investigated. All the experiments were performed at room temperature. The composites showed maximum dielectric constants of 24.42 and 37.6 at 1400 ℃ of 0.01 M concentration for titanium and strontium ions at 2 MHz, respectively. Due to the perfect nature of the doped mullite, it can be used for the fabrication of high charge storing capacitors and also as ceramic capacitors in the pico range.