LAUSR

Abstract A series of La+Nb co-doped TiO 2 (La 0.5 Nb 0.5 ) x Ti 1- x O 2 (0.25% ≤  x  ≤ 5%) ceramics were prepared using a solid-state reaction method. Colossal permittivity (CP) (eʹ > 10 4 ) and low dielectric loss (tanδ  2 atmosphere and annealed at 1073–1173 K in air. A pure rutile phase was achieved when x  = 0.25% and secondary phase La 2 TiO 5 was detected when x  ≥ 0.5%. The optimum dielectric performance of eʹ > 10 4 and tan δ x  = 0.5%. Three types of dielectric relaxations were observed through the dielectric-temperature spectrum: electron-pinned defect-dipoles (EPDD) polarization, electron hopping, and Maxwell–Wagner polarization. The CP (> 25 K at 1 kHz) was primarily related to EPDD polarization. The high activation energy of the grain boundary ( E gb  = 1.98 eV) is one of the reasons for the low tanδ in this study.