Abstract
A comparative study is carried out between the non-humidity sensitive Li vanadates, LiMnVO4 and LiCuVO4, from 25 to 500°C at frequencies from 42 Hz to 1 MHz. The mobile ion hopping rate of LiMnVO4 is found to be higher than that of LiCuVO4 due to the lower LiMnVO4 bulk and grain boundary activation energy values. Dielectric constant values from 25 to 500°C at frequencies from 42 Hz to 1 MHz revealed the presence of all types of polarisation. At the plots of LiCuVO4 tan δ (dielectric loss) versus frequency, tan δ displays a peak at a frequency that shifts to higher values with temperature. At 400°C, the maximum losses appear at 1 kHz and at 500°C at 10 kHz. The modulus master curves of LiCuVO4 and LiMnVO4 suggested the presence of conduction processes with the same activation energy at different frequencies.
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