An investigation on electrical properties of microwave treated natural ilmenite (FeTiO_3)

摘要

It has been observed that microwaves of 2.45 GHz heat dielectric materials. On subjecting natural ilmenite to microwave irradiation, the mineral is observed to heat, with a surface temperature in proportion to the irradiation time. With irradiation times from 40 to 240 seconds (increased in steps of 40 sec), the surface temperature measured on the samples were between 280 and 520 K. Electrical measurements made on the samples before and after irradiation show that the electrical properties are modified by the microwave irradiation. The real conductivity (σ′), dielectric constant (ɛ′) and the dielectric loss (ɛ″) plotted against frequency generally showed universal dielectric behaviour [1 and references therein] similar to that observed in other systems studied in the literature but using conventional heating techniques. Plots of σ′, ɛ′ and ɛ″ against the surface temperature of the sample showed frequency independent peaks around 460 K. The experimental dielectric loss (ɛ″) results fit a peak function of the form: $$varepsilon^{primeprime} = varepsilon_0 + frac{A}{omega_0 T {sqrt{2pi}}} exp left(-frac{big(lnbig(frac{T}{T_p}big)big)^2}{2omega_0^2}right) $$ where ɛ_0, A, and ω_0 are constants. The fitting of the dielectric loss results gives a frequency independent peak temperature (T_p) as 464 ± 5 K. Plotting the dielectric (γ′) and dielectric loss (γ″) exponents against temperature also gives an estimate of T_p close this value. The possibility of a ferroelectric transition in the samples is investigated by comparison with previous results obtained from synthetic ilmenite samples as it is the case with well known ferroelectric systems such as BaTiO_3[2].