Modeling the impedance of an electron-ionic conductor by taking into account the intercalation process

Based on visual observation of the WO3 electrochromism, a mathematical model of the intercalation process is built. It is shown that under certain conditions the capacitance of the sample becomes negative at ultralow frequencies. This effect is observed in the Bi2Mg0.5Cu0.5Nb2O9 solid solution at the temperature above 200A degrees C. The impedance studies of this compound confirm the coincidence of experimental and theoretical characteristics.