Abstract
Silicon carbide (SiC) has been synthesized by sol–gel technique by mixing 30 % mass ratio of silica nanoparticles with 70 % of resorcinol–formaldehyde the carbon precursor solution. After a drying phase, the sample was heated during two hours at different pyrolysis temperatures until 1400 °C in tubular furnace under open argon atmosphere. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy, current–voltage (I–V) and alternating current (ac) techniques in the temperature range between 80 and 300 K. Observations from the XRD for the sample prepared at 1400 °C, show three pronounced lines at 36°, 60° and 72° corresponding respectively to (111), (200) and (311) cubic β-SiC phase characteristic orientations. The temperature-dependence conductivities of the obtained structures show a semiconducting behavior and the I(V) characteristics present a negative differential resistance for all measurement temperatures between 80 and 300 K. The ac investigation was carried out for a wide range of frequency from 40 Hz to 110 MHz. The impedance plane plots show semicircle arcs at different temperatures. An electrical equivalent circuit has been proposed to explain the impedance results and the fundamental parameters of the circuit are determined at different temperatures in order to identify the contributions of the grains and boundary grains to the conductivity.