| Abstract | A series of resorcinol formaldehyde aerogels (RF aerogels) composite with nanoparticles of CoFe2O4havebeen prepared by sol–gel method. Four samples of pure RF aerogels were prepared at different concentra-tions of Na2CO3as catalyst (0.02, 0.025, 0.03, and 0.04 wt.%) and four samples of composite RF aerogelswere prepared at different concentration of doped CoFe2O4(0.075, 0.1, 0.125, and 0.15 wt.%; Na2CO3concentration = 0.03 wt.%). DC electrical conductivity as a function of temperature was studied in thetemperature range 25?C–200?C for all samples. AC electrical conductivity and dielectric properties weredetermined using RLC Bridge in the frequency range 100 Hz–1 MHz at different temperature (25–200?C).The pore size of the samples was determined using positron annihilation lifetime spectroscopy (PALS).RF aerogels are found to exhibit a semiconducting behavior and characterized by two transition temper-atures T1and T2. Also _DCincreases with increase of Co-ferrite contents. Pure RF aerogels posses a verylow dielectric constant, where the lowest value of ?_is ?4 times as that of air. ?_decreases with increaseof frequency, and increases with increase of temperature. Large overlapping polaron (OLP) is found tobe the preferred conduction mechanism in these materials. The results of PALS show that there are twotypes of pore size in these samples; the first ranges from 1.9 to 2.5 nm, while the second ranges from 3.2to 5.3 nm. |