Influence of CuO addition on the sintering temperature and giant dielectric properties of (In0.5Nb0.5)0.05Ti0.95O2 ceramics

Co-doped TiO2 ceramics exhibit great potential as high-performance giant dielectric materials. However, their excessively high sintering temperature renders them unsuitable for economical industrial production. The giant permittivity of these ceramics is closely correlated with the concentration of Ti3+ ions present. Adding a sintering aid to the ceramics is an effective method to reduce the sintering temperature. CuO, a common sintering aid, not only reduces the sintering temperature but also potentially enhances the Ti3+ ions concentration through the multivalence of Cu element, further optimizing their giant dielectric properties. Therefore, the effects of CuO addition on the sintering condition, microstructure, and dielectric properties of In and Nb co-doped TiO2 ceramics were investigated. The results indicate that CuO effectively lowers the sintering temperature of the ceramics. However, the presence of a large number of Cu+ ions inhibits the formation of Ti3+ ions, resulting in the disappearance of their giant dielectric properties. Upon annealing at 1150 degrees C for 2 h in air, the Ti3+ ions concentration significantly increases in the ceramics, consequently restoring their giant dielectric properties. Additionally, a new dielectric relaxation appears around 100 kHz, likely arising from the conductivity difference between the shallow layers and cores of grains induced by annealing. Furthermore, annealing enhances the grain boundary resistance, thereby reducing the low-frequency dielectric loss of the ceramics.