Variable Range Hopping Conduction in BaTiO₃ Ceramics Exhibiting Colossal Permittivity

Fast-fired barium titanate ceramics have been shown to exhibit room temperature colossal permittivity (ε r ′ ≈ 10 5, tan δ ≈ 0.05 at 1 kHz) when synthesized via the spark plasma sintering technique. Broadband dielectric spectroscopy analysis is here utilized to identify the active conduction mechanisms in the compound. Analysis of the temperature-dependent bulk dc conductivity reveals that the bulk conduction in fast-fired barium titanate is the result of variable-range hopping with relatively short hopping distance (∼0.5 nm) compared to other colossal permittivity materials. A common equivalent circuit that can model the contributions of the different polarization mechanisms to both the dc conductivity and colossal permittivity is established.