Electrical properties of Si4+ substituted copper ferrite

The electrical resistivity, , and Seebeck coefficient, , for the system Cu_1+xSi_xFe_2–2xO₄ (where x = 0.05, 0.1, 0.15, 0.2 and 0.3) have been studied as a function of temperature. Temperature variation of the resistivity exhibits two breaks. Each break is associated with a change in activation energy. The conduction process at low temperature is governed by the reaction Cu_A¹⁺+ Cu_A²⁺Cu_A²⁺+ Cu_A¹⁺. However, at higher temperature, it is due to intersite cation exchange and reoxidation such as Cu_A²⁺+ Fe_B³⁺ Cu_B²⁺+ Fe_A³⁺. Measurement of the Seebeck coefficient, , from room temperature to 800 K reveals n-type conduction for the sample with x= 0.05, while the measurements for other samples show p-type conduction for lower temperatures and n-type conduction at higher temperatures. The activation energies in the paramagnetic region are found to be less than those in the ferrimagnetic region.