title: Colossal Dielectric Behavior of Ga+Nb Co-Doped Rutile TiO2.
abstract: Stimulated by the excellent colossal permittivity (CP) behavior achieved in In+Nb co-doped rutile TiO2, in this work we investigate the CP behavior of Ga and Nb co-doped rutile TiO2, i.e., (Ga(0.5)Nb(0.5))(x)Ti(1-x)O2, where Ga(3+) is from the same group as In(3+) but with a much smaller ionic radius. Colossal permittivity of up to 10(4)-10(5) with an acceptably low dielectric loss (tan δ = 0.05-0.1) over broad frequency/temperature ranges is obtained at x = 0.5% after systematic synthesis optimizations. Systematic structural, defect, and dielectric characterizations suggest that multiple polarization mechanisms exist in this system: defect dipoles at low temperature (∼10-40 K), polaronlike electron hopping/transport at higher temperatures, and a surface barrier layer capacitor effect. Together these mechanisms contribute to the overall dielectric properties, especially apparent observed CP. We believe that this work provides comprehensive guidance for the design of new CP materials.
authors.forename: Wen
authors.initials: W
authors.lastname: Dong
authors.forename: Wanbiao
authors.initials: W
authors.lastname: Hu
authors.affiliation: The Bragg Institute, Australian Nuclear Science and Technology Organisation , New Illawarra Road, Lucas Heights, Sydney, New South Wales 2234, Australia.
authors.forename: Adam
authors.initials: A
authors.lastname: Berlie
authors.forename: Kenny
authors.initials: K
authors.lastname: Lau
authors.forename: Hua
authors.initials: H
authors.lastname: Chen
authors.forename: Ray L
authors.initials: RL
authors.lastname: Withers
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu
keywords: ceramic; colossal permittivity; defect dipole; dielectric properties; rutile TiO2