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.

Dielectric properties of Y and Nb co-doped TiO2 ceramics

“…Additionally, Fig. 4(b) depicts that there should be a dissipation peak shifting to higher frequency with the increasing of temperature, which is in correspondence to the Debye relaxation 1, 3, 9, 25–27 . The dielectric relaxation time (τ) could be calculated with the extreme value relationwhere circular frequency ω p equals to 2πf p and f p is the characteristic frequency at the peak of tan δ.…”

“…The dielectric relaxation time (τ) could be calculated with the extreme value relationwhere circular frequency ω p equals to 2πf p and f p is the characteristic frequency at the peak of tan δ. The fast increase of f p indicates the decrease of τ with temperature increase, which is due to the thermally excited relaxation process 1, 3, 7, 24 . The activation energies required for these relaxations can be calculated with the Arrhenius law aswhere τ 0 is the pre-exponential factor, E a is the activation energy for the relaxation, K B is the Boltzmann constant, and T is the temperature corresponding to the peak of tan δ.…”

“…The CP behavior of materials can be explained on the basis of semiconducting grains and insulating grain boundaries 15–17 . There are other mechanisms used to explain the overall dielectric response in TiO 2 -based ceramics, including electron hopping 18 and non-Ohmic sample-electrode contact 3 . In addition, following researches introduced more similar types of ceramics such as Ga+Nb and Al+Nb co-doped TiO 2 2–4, 14 .…”

“…In addition, following researches introduced more similar types of ceramics such as Ga+Nb and Al+Nb co-doped TiO 2 2–4, 14 . However, both of the Ga+Nb and Al+Nb co-doped rutile TiO 2 ceramics were also reported to show poor dielectric properties compared with the In+Nb co-doped in TiO 2 ceramics 1, 3, 4, 13, 16, 17, 19–21 . Thus, developing more acceptor/donor for the AB co-doped rutile TiO 2 ceramics is essential for pursuing high quality colossal permittivity ceramic materials.…”

Dielectric properties of manganese-doped TiO2 with different alkali-free glass contents for energy storage application

“…Unlike ferroelectric material such as BST, it had a higher energy efficiency on energy charge-discharge [10,17]. However, due to processing conditions, a small amount of oxygen vacancies as donor impurities often existed in titanium dioxide, which could increase dielectric loss and reduce breakdown strength [18][19][20][21][22]. Therefore, in this study, we chose acceptor (manganous)-doped titanium dioxide as the dielectric ceramic, the effect of different additive amounts of alkali-free glass on the dielectric properties of Mn-doped TiO 2 was investigated for its energy storage applications.…”