Internal barrier layer capacitor, nearest neighbor hopping, and variable range hopping conduction in Ba_1−xSr_xTiO_3−δ nanoceramics

The dielectric properties of the solid solution Ba_1−xSr_xTiO_3−δ (0 ≤ x ≤ 1) have been investigated. The nanopowders were prepared via a coprecipitation reaction followed by a calcination treatment. Spark plasma sintering allowed to obtain dense nanocrystalline ceramics. Broadband impedance spectroscopy revealed colossal permittivity (ε′ = 10⁵) associated with low losses (tan δ = 0.03) in the most favorable case. The bulk conductivity data was analyzed using Jonscher’s universal dielectric response model. In the Ba-rich compound, conduction process followed variable range hopping conduction model while the Sr-rich BST compound showed the nearest neighbor hopping conduction mechanism associated with displacements of space charges. These two different conduction mechanisms might be able to explain superior temperature–frequency-independent dielectric properties in Sr-rich BST compound compared to Ba-rich BST compound.