Abstract
Impedance spectroscopy has been used to investigate a correlation between the microstructure and electrical properties of a phase-separated Li(Fe0.5Al0.5)5O8 solid solution. The phase separation of the Li(Fe0.5Al0.5)5O8 single-phase solid solution, which was caused by annealing at 1000°C, resulted in a continuous compositional variation, suggesting that the phase separation proceeded spinodally. An equivalent circuit proposed for modeling a modulated microstructure of the spinodally decomposed Li(Fe0.5Al0.5)5O8 successfully explained the change in the electrical properties during the phase separation. Impedance and electric modulus data suggested that a well-defined phase boundary between separated phases was formed after annealing for 40h. The bulk conductivity was dominated by the Fe-rich phase at the early stage of the phase separation, whereas the conductivity of the phase boundary was dominant after its formation. For interpreting the electric modulus spectra, the activation energy of its peak frequency was useful.
