Impedance spectroscopic study on nanocrystalline Ce0.75Zr0.25O2 ceramics

The effect of the grain size on the dielectric properties and electrical conductivity was studied for single-phase solid solution of the ZrO₂–CeO₂ system with 75% CeO₂. The bi-ceramic composition of ZrO₂–CeO₂ as Ce_0.75Zr_0.25O₂ was prepared through a solid-state reaction to synthesize single-phasic material followed by high-energy ball milling to make finer particle size. Structural properties were confirmed through advanced analytical techniques such as XRD and Raman spectroscopy. SEM confirmed large porosity with a grain size of 204 ± 3 nm, which is larger than the crystallite size of 22.64 ± 8.6 nm calculated from the XRD analysis for Ce_0.75Zr_0.25O₂. The dielectric measurements were performed as a function of temperature by impedance spectroscopy. The relative dielectric constant decreases on increasing frequency for all temperatures, which validates the polar nature of nanocrystalline Ce_0.75Zr_0.25O₂ ceramic. In addition, temperature-dependent enhancement in \({\varepsilon }_{\text{r}}\) is more pronounced in low-frequency regions due to low-frequency dielectric dispersion phenomena. The dielectric loss also increases with increasing temperature over the frequency region from 100 Hz to 2 MHz. The electrical conductivity of nanocrystalline Ce_0.75Zr_0.25O₂ was found to be smaller than the micron-sized sample of Ce_0.75Zr_0.25O₂. The present study revealed the crucial role of grain size in tuning the dielectric properties of Ce_0.75Zr_0.25O₂ along with ac conductivity.