Successive Phase Transitions and Their Soft Modes in Ferroelectric Sr₂Nb₂O₇

Abstract

The soft optic modes responsible for the successive phase transitions of Sr2Nb2O7 have been observed by the Raman scattering measurement. The characteristics of the soft modes are discussed in connection with the macroscopic properties of the successive phase transitions.

Electronic and vibrational properties of the low-dimensional perovskitesSr1−yLayNbO3.5−Kuntscher1, Schuppler2, Haas3 et al. 2004Phys. Rev. B152190View full textAdd to dashboardCite

“…Interestingly, the relatively strong modes observed in SrNbO 3.50 around 110 and 170 cm mode was assigned to the soft mode of the ferroelectric phase transition at 1615 K, based on Raman scattering experiments. 16 It was also observed in recent optical measurements and related to NbO 6 octahedra tiltings. 17 In agreement with Ref.…”

Normal-incommensurate phase transition in (Sr1−xBax)2Nb2O7ferroelectric single crystals

“…In the scenario observed here, T i decreases and also the concentration of the IC phase lowers (as seen by slope variations in Fig. 2), what happens to the R soft mode [5] that exists only in the IC phase (responsible for the low temperature dielectric anomaly at wK177 8C) is not so clear. It is anticipated that due to substitution of larger atom (Ba) on A-site the tilting of the oxygen octahedra is suppressed that affects T i markedly.…”

“…This transition was observed in the elastic compliance coefficients, electromechanical coupling, permittivity, and birefringence. The lattice instability studies revealed the soft optic modes responsible for the first and second phase transitions, and for the normal-IC phase transition [5]. As for Ba doped (Sr 1K…”

Low temperature hydrothermal synthesis, characterization and optical properties of strontium pyroniobate

“…Only n = 4 and n = 5 members of the series have been observed so far [22][23][24]. By Cooling from above the Curie temperature, [25] Sr 2 Nb 2 O 7 undergoes the ferroelectric phase transition from space group Cmcm to Cmc2 1 , which is commonly referred to as the normal orthorhombic phase. On further cooling to 215°C, the compound changes to an incommensurate (IC) phase with space group Cmc2 1 [26,27].…”