Microscopic ion migration in solid electrolytes revealed by terahertz time-domain spectroscopy

Terahertz spectroscopy is one of the most suitable methods for the analysis of electron transport in solids, and has been applied to various materials. Here, we demonstrate that terahertz spectroscopy is the technique of choice to characterize solid electrolytes. We measure the terahertz conductivity of stabilized zirconia, a widely used solid electrolyte material, by terahertz time-domain spectroscopy at high temperatures, providing a wealth of information unavailable from conventional techniques. It is found that the conductivity reflects the microscopic motion of the ion just before hopping to an unoccupied site. Our results suggest a powerful approach in probing the ionic conduction mechanism and could help us explore other solid electrolytes for fuel cells and all-solid-state batteries. Here the authors expand the application scope of terahertz spectroscopy to the characterization of electrolyte materials. Based on the measurement of the conductivity of yttria-stabilized zirconia in the terahertz frequency range, unprecedented insight into the microscopic motion of the ion is revealed.