Electric field and aging effects of uniaxial ferroelectrics SrxBa1\u2212xNb2O6 probed by Brillouin scattering

M Aftabuzzaman,W Kleemann,J Dec,M A Helal,R Paszkowski,S Kojima

doi:10.1038/s41598-017-10985-9

Abstract

Static and dynamic heterogeneity of disordered system is one of the current topics in materials science. In disordered ferroelectric materials with random fields, dynamic polar nanoregions (PNRs) appear at Burns temperature and freeze into nanodomain state below Curie temperature (TC). This state is very sensitive to external electric field and aging by which it gradually switches into macrodomain state. However, the role of PNRs in such states below TC is still a puzzling issue of materials science. Electric field and aging effects of uniaxial ferroelectric SrxBa1−xNb2O6 (x = 0.40, SBN40) single crystals were studied using Brillouin scattering to clarify the critical nature of PNRs in domain states below TC. On field heating, a broad anomaly in longitudinal acoustic (LA) velocity at low temperature region was due to an incomplete alignment of nanodomains caused by the interaction between PNRs. A sharp anomaly near TC was attributed to the complete switching of nanodomain to macrodomain state owing to the lack of interaction among PNRs. After isothermal aging below TC, the noticeable increase of LA velocity was observed. It was unaffected by cyclic temperature measurements up to TC, and recovered to initial state outside of a narrow temperature range above and below aging temperature.

Highlights

The role of polar nanoregions (PNRs) in such states below TC is still a puzzling issue of materials science
The existence of the transverse acoustic (TA) mode in all temperature regions above and below TC observed at c(a, a + b)c geometry indicates that the SBN40 single crystal belongs to the tetragonal symmetry both in paraelectric and ferroelectric phases
TC, the noticeable difference between zero field heating (ZFH) and zero field cooling (ZFC) is due to the metastable irreversible domain structure caused by an incomplete switching of nanodomains induced by quenched random fields (RFs) during the cooling process[54, 55]

Summary

Introduction

The role of PNRs in such states below TC is still a puzzling issue of materials science. Uniaxial REFs with tetragonal tungsten bronze (TTB) structure such as SrxBa1−xNb2O6 (SBN) are technologically important materials owing to their remarkably high dielectric, piezoelectric, pyroelectric, and photorefractive properties[5,6,7,8,9,10,11,12]. These excellent physical features are useful for modern applications such as sensors, data storage[8, 11, 13,14,15,16], lasers, and holography[17, 18]. It is considered that the PNRs play a vital role in the relaxor behavior by inducing the diffusive and frequency-dispersive dielectric anomalies and various precursor phenomena[37, 38]

Methods

Results

Conclusion