High density (95–97%) Lax () ceramics were tested for structural and dielectric properties. Dense microstructure and controlled phase-purity were obtained for all the -doped samples. A surprising three-fold increase was noticed in the frequency dependent dielectric permittivity behavior for the ceramic, associated with the space-charge polarization at grain boundaries or inhomogeneous microstructure of the ceramic. High resistivity (∼108 Ωm) at room temperature was noticed for the ceramics (at 100 Hz). Hopping of electrons within the oxygen vacancies were noted as the main transport mechanism; strong localization of charge carriers were noticed at high frequencies. The temperature dependent ac-resistivity analysis (T) provides strong evidence for Mott’s variable range hopping process of charge carriers, between the localized states with an average hopping length of RH of 3 nm and hopping energy of WH of 0.67 eV. Moreover, the effect of grains and grain boundaries on the correlation between ac-conductivity and angular-frequency ω has been discussed in detail.