Reinvestigation of conducting properties of Ca-doped barium titanate

Relaxation processes of Ba1- xCaxTiO3 ceramics with x = 0.05, 0.10 and 0.23 Ca contents were studied by combining the dielectric modulus and complex impedance experiments. Use of both methods permits an exploration of relaxation processes in both time and frequency domains, including relaxation distribution function at low and high frequency relaxation regions (grain and grain boundary). From an analysis using the complex impedance formalism, the predominant time distribution relaxation function turns out to be a Cole-Cole type, whereas from the dielectric modulus formalism it is described by non-Debye relaxation functions. While activation energies derived from the dielectric modulus formalism are characteristic of doubly-ionized oxygen vacancies (0.85-1.00 eV), they are from the complex impedance approach expressed as a typical electronic conduction (1.2-1.5 eV). It was identified that the impedance formalism describes well the relaxation in the low frequency regime with similar activation energy derived from the Jonscher power law (1.1-1.4 eV). The present study highlights the potential of using both impedance and dielectric modulus formalisms to identify and quantify non-Debye relaxation process and conducting properties in mixed electronic-ionic conductors.

Automated summary

The relaxation processes of Ba1-xCaxTiO3 ceramics with different Ca contents were studied using dielectric modulus and complex impedance experiments. Both methods provided insights into relaxation processes in both the time and frequency domains. The complex impedance formalism revealed a Cole-Cole type relaxation function, while the dielectric modulus formalism described non-Debye relaxation functions. The activation energies derived from these methods differed, with the dielectric modulus formalism indicating doubly-ionized oxygen vacancies and the complex impedance approach suggesting electronic conduction. The study also demonstrated the effectiveness of using both impedance and dielectric modulus formalisms to analyze non-Debye relaxation processes and conductive properties in mixed electronic-ionic conductors.