Dielectric properties and impedance analysis in Aurivillius-type (Na0.25K0.25Bi0.5)1−x(LiCe)x/2[]x/2Bi4Ti4O15 ceramics

► LiCe modified Na0.25K0.25Bi4.5Ti4O15 ceramics have been prepared. ► Dielectric and impedance properties at high temperature were characterized using the impedance spectrum technique. ► Different polarization mechanisms were found below and above TC according to the Landau free energy model. ► AC electrical conductivity exhibits different behaviors at elevated temperature.