Temperature- and Frequency-Dependent Dielectric Properties of Sol–Gel-Derived BaTiO₃-NaNbO₃ Solid Solutions

Abstract

A sol–gel-derived powder synthesis method has been used to prepare BaTiO₃-NaNbO₃ (BT-NN) solid-solution ceramic samples with various compositions. Fine and homogeneous complex perovskite ceramics were obtained at lower processing temperatures than used in conventional solid-state processing. The ferroelectric and relaxor ferroelectric properties of the sol–gel-synthesized (1 − x)BaTiO₃-xNaNbO₃ [(1 − x)BT-xNN] ceramics in the wide composition range of 0 < x ≤ 0.7 were extensively studied. Structural and dielectric characterization results revealed that a low level of NN addition (x = 0.04) to BT is sufficient to cause a continuous relaxor-to-ferroelectric transition, and the relaxor behavior was consistently observed at compositions with high NN content up to x = 0.7. A number of relaxor parameters including the Curie temperature, Burns temperature, freezing temperature, γ, diffuseness parameter (δ), and activation energy were determined from the temperature and frequency dependency of the real part of the dielectric permittivity for various BT-NN compositions using the Curie–Weiss law and Vögel–Fulcher relationship. The systematic changes of these parameters with respect to composition indicate that a continuous crossover between BT-based relaxor and NN-based relaxor occurs at a composition near x = 0.4.