Phase Separation and Electrical Properties of the Li(Fe_(0.5)Al_(0.5))_5O_8 Spinel Solid Solution

摘要

Impedance spectroscopy has been used to investigated a correlation between the microstructure and electrical properties of a phase-separated Li(Fe_90.5)Al_(0.5))_5O_8 solid solution. The phase separation of the Li(Fe_90.5)Al_(0.5))_5O_8 single-phase solid solution, which was caused by annealing at 1000deg 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(Fe_90.5)Al_(0.5))_5O_8 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 phase was formed after annealing for 410 h. 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.