Effect of sintering aid (CoO) on transport properties of nanocrystalline Gd doped ceria (GDC) materials prepared by co-precipitation method

Electrical and dielectric properties of the nanocrystalline GDC materials co-doped with CoO (by deposition precipitation method) were studied in the temperature range of 150-600 °C. CoO co-doped samples show higher grain interior conductivity than that of GDC. Dielectric loss tangent (tan δ) shows the presence of defect associates such as (Co-Vo¨-Co) and (Co-Vo¨) in co-doped samples in addition to the defects (Gd-Vo¨-Gd) and (Gd-Vo¨) that are present in GDC system. Dynamic parameters such as migration energy and association energy of oxygen vacancies do not vary significantly with co-doping CoO in the GDC materials. With higher content of CoO, excess of Co2+ in the grain boundary regions leads to trapping of vacancies and/or depletion of vacancies in the space charge region. Therefore grain boundary activation energy increases and grain boundary conductivity decreases with CoO content above 1 mol%, at lower temperatures. In the temperature range of 150-600 °C overall conductivities in CoO co-doped samples increase two to three times than that of GDC material.