The analysis of charge transport mechanism in mixed ionic electronic conductor composite of Sr2TiCoO6 double perovskite with yttria stabilized zirconia

In this investigation, the ionic conduction mechanism in mixed ionic electronic conductors composites of Sr2TiCoO6/YSZ has been studied with the help of universal dynamic response. 3 mol% and 8 mol% yttria stabilized ZrO2 have been mixed with Sr2TiCoO6 (STC) double perovskite in 1:1 ratio to prepare STC/3YSZ and STC/8YSZ composites via solid-state reaction route. AC Impedance spectroscopy has been carried out to examine the charge transport mechanism, which has been modeled using the microstructural networks of resistors and capacitors. Grain boundaries are more resistive and capacitive compared to the bulk. Modulus spectroscopy analysis demonstrates the non-Debye character of conductivity relaxation with frequency. Complex frequency-dependent AC conductivity is found to obey Almond West power law and reveals that ion migration occurs through the correlated hopping mechanism. Further, the DC conductivity and relaxation time have been found to follow the Barton Nakajima and Namikawa relation, which is correlated with AC to DC conduction. The time-temperature superposition principle has been used to explain the conductivity scaling in the intermediate frequency range. At low temperatures, the ions are localized in the asymmetric potential well, while at high temperatures, hopping behavior starts dominating. Further Kramers-Kronig transformation connects the dielectric strength with conductivity relaxation and verifies the impedance data.