Electrical resistivity of NiFe_2O_4 ceramic and NiFe_2O_4 based cermets

NiFe2O4 ceramic and NiFe2O4 based cermets, expected to be used as the inert anodes in aluminum electrolysis, were prepared and their electrical resistivities were measured at different temperatures. The effects of temperature and composition on their electrical resistivities were investigated. The results indicate that the electrical resistivities of NiFe2O4 based cermets mainly depend on temperature, resistivity of ceramic matrix, composition and dispersion of the metal phase among ceramic matrix. The electrical resistivity of NiFe2O4 ceramic decreases from 10.094 Ω·cm to 0.475 Ω·cm with increasing temperature from 573 K to 1 233 K. The electrical resistivities of NiFe2O4 based cermets are greatly lowered, but decrease with increasing the temperature with similar trend compared to that of NiFe2O4 ceramic. The resistivities of NiFe2O4 based cermets containing 5% Ni, 5% Cu and 5% Cu-Ni alloy are 0.046 8, 0.066 8 and 0.0532 Ω·cm at 1 233 K, respectively, which are all acceptable as inert anode materials compared to that of the current carbon anode used for aluminum electrolysis.