High permittivity Li and Al doped NiO ceramics

High-permittivity dielectric NiO-based ceramics co-doped with Li and Al (LANO) have been prepared by a traditional solid-state synthesis. Analyses of the ceramic microstructure and composition indicate that Al ions are distributed in grain boundaries, and that uniform boundaries indexed as NiAl2O4 surround the grains. The concentration of Al has a remarkable effect on the dielectric properties of the LANO ceramics. The dielectric constant remains almost constant (∼104–105) at low frequency and has a steplike decrease toward higher frequencies. The high-dielectric-constant response of the LANO ceramics is mainly enhanced by Maxwell–Wagner polarization.