Effect of Ta substitution on the ferroelectric-antiferroelectric phase transition in tetragonal tungsten bronze-type K₂NdNb₅O₁₅

Antiferroelectric (AFE) materials have attracted considerable attention for applications in energy-storage dielectric capacitors. From the viewpoint of energy efficiency, AFEs with slim polarization (P)–electric field (E) hysteresis are desirable. Herein, we focused on tetragonal tungsten bronze-type K2NdNb5O15 as a candidate for such a material and aimed to control its ferroelectric (FE)–AFE phase transition temperature to obtain the AFE phase at room temperature. In this study, K2Nd(Nb1−xTax)5O15 (x = 0–0.20) ceramics were prepared using a solid-state reaction method, and their dielectric properties were evaluated. It was established that the incorporation of Ta lowered the FE-AFE phase transition temperature, and the AFE phase was obtained at room temperature for x = 0.15 and 0.20. Through P-E measurements, narrow P-E double hysteresis loops were observed for x = 0.15 and 0.20. These results provide insight into controlling the temperature range of the AFE phase of K2NdNb5O15 to around room temperature.