Conductivity and impedance spectroscopic studies of self-sustained high-temperature synthesized nano-Ce1-xGdxO2-δ solid solutions

Despite extensive research on CeO2 in diverse fields, studies on dielectric, conductivity behaviours due to intentional impurity-induced structural and microstructural changes are not well established. We show that structural changes arising due to Gd3+ in nano-CeO2 and the temperature affect the dielectric and conductivity characteristics. Highly crystalline nano-CeO2 and Ce1-xGdxO2-δ (GDC) (x = 0.02–0.1) are synthesized by self-sustained high-temperature synthesis. The dependence of conductivity on dopant concentration is examined over a wide-frequency (20 Hz to 10 MHz) and temperature (200–800 °C) range using a precision impedance analyzer. The conductivity reaches maximum at x = 0.06 for Ce1-xGdxO2-δ at 600 °C beyond which conductivity decreases. There is dependence of conductivity at lower frequencies, increases with increasing frequency, and gets saturated at higher frequencies. The optimum concentration (x = 0.06) found is the lowest for the Ce1-xGdxO2-δ system reported. The observed behaviour is discussed in terms of interaction between oxygen vacancies and defect associates.