The colossal dielectric properties of FeNbO4

The dielectric properties of FeNbO4 ceramics were systematically investigated in the frequency range from 100 Hz to 5 MHz and temperature from 75 to 300 K. It is observed that the sample exhibits colossal dielectric behavior and three dielectric relaxations. Both the low- and middle-temperature relaxations were found to be bulk effect related to localized carriers hopping. It is revealed that the low temperature relaxation is caused by the hopping motion of the self-trapped electrons and the middle temperature relaxation is related to the electrons hopping between Fe2+ and Fe3+ ions. By means of complex impedance analysis the high-temperature relaxation was argued to originate from Maxwell-Wagner relaxation due to grain boundary response.