Grain size engineering in nanocrystalline Y2Zr2O7: A detailed study on the grain size correlated electrical properties

Abstract A set of nanocrystalline Y2Zr2O7 (YZO) ceramic materials possessing grain sizes ranging from 7 nm to 65 nm was prepared by chemical co-precipitation technique followed by conventional sintering at various temperatures. Evolution of structure and grain growth was investigated by XRD and TEM analysis. Disordered pyrochlore phase of YZO was obtained. Electrical conductivity of YZO has been increased with increasing measuring temperature as well as grain size. The behavior of total electrical conductivity comprising grain interior and grain boundary components was studied. When the grain size was increased, the activation energy for grain boundary and total ionic conduction has been decreased from 1.59 to 1.51 eV whereas the same for bulk grain conductivity remained more or less the same near to 1.43 ± 0.01 eV. The Jonscher's universal law had explained the behavior of ac conductivity suggesting a long-range hopping of mobile ions-based conduction in YZO. In addition, Maxwell–Wagner model had explained the dielectric behavior of YZO and showed an increasing dielectric constant with increasing grain size. Electric modulus, analysed by Kohlrausch-Williams-Watts function, showed an increasing relaxation frequency at higher grain sizes. A complete electrical characterization of YZO ceramics with good correlation with their grain size is reported.