Coupling Between Octahedral Tilting and Ferroelectric Order in Tetragonal Tungsten Bronze-Structured Dielectrics
Igor Levin, M Stennett, D I. Woodward, A R. West, I Reaney
Strong coupling between local polar displacements and a commensurate octahedral tilting is proposed to explain the onset of classic ferroelectric behavior in tetragonal tungsten bronze-like dielectrics BaLaxNd1-xNb3Ti2O15. The ferroelectric phase transition is associated with a discontinuous non lock-in transformation of an incommensurate structure described by the wave vectors q1=( +?)(ao*+bo*), q2= co to a commensurate superstructure with q1= (ao*+bo*), q2= co*, where ao bo 12.4 and co 4 refer to an ideal tetragonal tungsten bronze cell. In a manner reminiscent of perovskite-like oxides, the driving force for commensurate tilting increases as the average ionic radius of the rare-earth ion decreases, and no classical ferroelectric transition is observed for compositions with x>0.75 which remain incommensurate and only exhibit relaxor behavior below room temperature.
, Stennett, M.
, Woodward, D.
, West, A.
and Reaney, I.
Coupling Between Octahedral Tilting and Ferroelectric Order in Tetragonal Tungsten Bronze-Structured Dielectrics, Applied Physics Letters
(Accessed June 2, 2023)