Normal-incommensurate phase transition in (Sr_1−xBa_x)₂Nb₂O₇ferroelectric single crystals

Abstract

Micro-Brillouin and Raman light scattering experiments were performed on (Sr 1Kx Ba x ) 2 Nb 2 O 7 single crystals to investigate the effect of Ba addition on the normal-incommensurate phase transition. From the Brillouin frequency shift results, it was observed that the onset temperature of the normal-incommensurate phase decreased with increasing Ba concentration. This was associated to the suppression of the octahedra tilting due to substitution of larger ion on the A-site. The Raman intensity of the Q soft mode measured at room temperature also showed a similar behaviour with increasing x. q

High-pressure structural change in the ferroelectric layered perovskite Sr2Nb2O7

“…In the case of SNO, f1 drastically decreases this dependence with pressure. This low-dependence behavior in f1 can be explained with the reported effects of Ba substitution on Sr 2 Nb 2 O 7 to form Sr 2−x Ba x Nb 2 O 7 [32], where the substitution does not significantly change the frequency of the f1 phonon. Additionally, the substitution of Ba decreases the NbO 6 R x rotations, as observed through the reduction of the spontaneous polarization [33].…”

Structural and Raman study of the thermoelectric solid solution Sr1.9La0.1Nb2O7

“…As is well known in Raman spectroscopy [ 32 ] and reported by Kojima et al (Sr 2 Nb 2‐x Ta x O 7 ) [ 33 ] and Shabbir et al (Sr 2−x Ba x Nb 2 O 7 ) [ 34 ] for longitudinal acoustic phonons in the vicinity of the IC transition temperature T i−c , second‐order phase transitions may reflect a change in the temperature wavenumber coefficient of some Raman bands or the gradual but final disappearance of some Raman bands at the phase transition critical temperature. This originates from a Raman‐active order parameter, collective excitation in the transforming structure, or phonon lines that are either permitted or forbidden in the new crystalline structure adopted by the compound after the transition.…”

“…Examples of this include the substitution of Ba ions for Sr ions to form Sr 2−x Ba x Nb 2 O 7 ( x ≤ 0.32). [ 34 ] Ion substitution decreases T i−c , possibly due to the larger ionic radius of Ba compared to Sr. In SLNO1, the increased T i−c may be caused by the less distorted misaligned NbO 6 octahedra (generated by the additional charge provided).…”

“…This has been reported under atmospheric pressure and room temperature conditions for n = 4 Brandon–Megaw compounds. [ 34,38–42 ] We identify SLNO1 temperature and pressure phase transitions at T = 247°C ± 5°C and P = 6.74 ± 0.25 GPa, respectively. Both transitions seem to correspond to the IC ‐ to‐commensurate Cmc 2 1 transition.…”

Crystallization Atmosphere and Substrate Effects on the Phase and Texture of Chemical Solution Deposited Strontium Niobate Thin Films

“…Layered perovskites, such as strontium niobate, have recently received attention as potential candidates for high‐temperature ferroelectric, piezoelectric, and thermoelectric materials. Many of these complex oxides are attractive thermoelectric materials due to their thermal stability, ability to accommodate a wide variety of dopant elements, and low thermal conductivity .…”