Ac conductivity and dielectric properties of CuFe1xCrxO2:Mg delafossite

M Lalanne (1) , P Demont (1) , A Barnabé (1)

1 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux

The electrical and dielectric properties of CuFe 1-x Cr x O 2 (0 x 1) powders, doped with 3 % of Mg and prepared by solid-sate reaction, were studied by broadband dielectric spectroscopy in the temperature range from -100 to 150°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 CuFe 1-x Cr x O 2 powders. The substitution of Fe 3+ by Cr 3+ results in an increase of dc conductivity and a decrease of the Cu + -Cu + distance. Dc conductivity, characteristic onset frequency and Havriliak-Negami characteristics relaxation times are thermally activated above -40°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 CuFe 1-x Cr x O 2 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°C respectively.

Mots clés: Physical Sciences

M Lalanne, P Demont, A Barnabé. Ac conductivity and dielectric properties of CuFe1xCrxO2:Mg delafossite. Journal of Physics D: Applied Physics, 2011, 44 (18), pp.185401. ⟨10.1088/0022-3727/44/18/185401⟩. ⟨hal-00629939⟩