Maxwell–Wagner effect in hexagonal BaTiO3 single crystals grown by containerless processing

Oxygen-deficient hexagonal BaTiO3 single crystals, with dielectric constant ε′∼105 and loss component tan δ∼0.13 at room temperature and a linear temperature dependence of ε′ in the range 70–100K, was analyzed by impedance spectroscopy analysis. Two capacitors, bulk and interfacial boundary layer, were observed, and the colossal dielectric constant was mainly dominated by the interfacial boundary layers due to Maxwell–Wagner effect. After annealing the oxygen-deficient hexagonal BaTiO3 at 663K, the ε′ and tanδ became, respectively, 2×104 and 0.07 at room temperature. This work showed an important technological implication as annealing at lower temperatures would help to obtain materials with tailored dielectric properties.