Local structure and dielectric behavior of tetragonal tungsten bronzes β-SrTa₂O₆ and β′-SrTa₂O₆

Abstract

The dielectric properties of polymorphic tungsten-bronzes, β-SrTa₂O₆ and β′-SrTa₂O₆, were measured using phase pure ceramic specimens. The room temperature dielectric constant (κ) of β-SrTa₂O₆ and β′-SrTa₂O₆ were ≈26 and ≈104, respectively, which were relatively constant over the ac frequency range, 10²–10⁶ Hz. The markedly distinct κ of β- and β′-SrTa₂O₆ were attributed to local structural details, where the displacive Sr disorder in β′-SrTa₂O₆ was emphasized. Both β- and β′-SrTa₂O₆ exhibited a temperature dependent transition of κ with diffuse maxima at 40–80 K.