Studies on the Eutectoid Decomposition of CuFe₅O₈ by Electrical Resistivity Measurement

Abstract

The eutectoid decomposition of CuFe₅O₈ into CuFeO₂ and Fe₂O₃ has been studied by electrical resistivity measurement of the sintered bodies during heating and cooling in the temperature range between 200°C and 1050°C, and it is shown that this method provides useful information in some solid state processes.
The apparent decomposition temperature as detected by an abrupt increase in resistivity depends on the rate of temperature change, more strikingly in cooling than in heating. The resistivity after the decomposition decreased with decreasing rate of cooling, which has been interpreted in terms of the dispersion of the decomposition products; the pearlitetype structures obtained at low cooling rates give lower resistivity than the bainite-ones. No significant effect of heating rate on the resistivity after the decomposition as well as on the microstructure has been observed. Substitution of CuFe₂O₄ and Fe₃O₄ was found to check the decomposition.