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摘要
The electrical and dielectric properties of CuFe1-xCrxO2 (0 <= x <= 1) powders, doped with 3% of Mg and prepared by solid-state reaction, were studied by broadband dielectric spectroscopy in the temperature range from -100 to 150 degrees C. The frequency-dependent electrical and dielectric data have been discussed in the framework of a power law conductivity and complex impedance and dielectric modulus. At room temperature, the ac conductivity behaviour is characteristic of the charge transport in CuFe1-xCrxO2 powders. The substitution of Fe3+ by Cr3+ results in an increase in dc conductivity and a decrease in the Cu+-Cu+ distance. Dc conductivity, characteristic onset frequency and Havriliak-Negami characteristics relaxation times are thermally activated above -40 degrees C for x = 0.835. The associated activation energies obtained from dc and ac conductivity and from impedance and modulus losses are similar and show that CuFe1-xCrxO2 delafossite powders satisfy the BNN relation. Dc and ac conductivities have the same transport mechanism, namely thermally activated nearest neighbour hopping and tunnelling hopping above and below -40 degrees C, respectively.
- 出版日期2011-5-11
