Temperature Dependent Relaxation Behavior of Polycrystralline LuFe₂O₄ Studied By Dielectric Spectroscopy

Polycrystalline LuFe₂O₄ ceramics was synthesized by solid state reactions at 1200°C with a mixed gas flow of CO₂ and H₂. The temperature dependence of zero-field cooled and field-cooled magnetization measurements indicates a clear paramagnetic to ferromagnetic transition in our LuFe₂O₄ samples. The temperature relaxation behavior of LuFe₂O₄ ceramics was investigated by an impendence analyzer in the frequency range from 20 Hz to 1 MHz. The contributions of grain boundaries, bulks, and electrodes to the ac conductivity and relaxation processes were identified by fitting the impendence data with an equivalent circuit model. When the temperature is lower than around 220 K, the bulk effect dominates over the contributions of grain boundaries and electrodes on the dielectric relaxation process. However, when the temperature is higher than 220 K, the electrode effect becomes dominant. The polycrystalline LuFe₂O₄ also show a temperature dependent activation energies for ac conductivities which may relate to non-stoichiometric oxygen deficiency in our samples.

Keywords:

• LuFe₂O₄ ceramic
• relaxation
• oxygen deficiency