Spectroscopic properties and dielectric dispersion of K2O-BaO-B2O3 glasses doped with Fe2O3

Alkali borate glasses doped with different concentrations of ferric oxide in the range 0-1 mol % in steps of 0.2 mol % have been prepared. The dielectric properties, especially dielectric constant epsilon', loss tan delta a c conductivity sigma(ac) over a wide range frequency (1-100 kHz) and temperature (30-300 degrees C), ESR and IR spectra of Fe2O3 containing K2O-BaO-B2O3 glasses have been studied. The dielectric study reveals that the glasses have high insulating strength when Fe2O3 concentration is 0.8 mol % in the glass matrix. The results have been analyzed in the light of different oxidation states of iron ions with the help of IR and ESR spectra data. The analysis indicates that when the concentration of iron ions is up to 0.8 mol %, these ions exist in Fe3+ state that takes modifier as well as network former position, beyond this concentration some of the iron ions switch over from Fe3+ to Fe2+ state that takes network modifier positions and weakens the insulating strength of the glass.