Precession Electron Diffraction Studies of Sr x Ba 1-x Nb 2 O 6 and Ca x Ba 1-x Nb 2 O 6 Single Crystals

Dec

Kleemann

et al. 2018

Jpn. J. Appl. Phys.

The electric field effects on the acoustic properties of uniaxial ferroelectric SrxBa1−xNb2O6 (x = 0.40, SBN40) crystals with weak random fields were studied by Brillouin scattering. On field cooling, the minimum of longitudinal acoustic (LA) velocity shifted to a higher value and a marked increase in LA velocity was observed below the Curie temperature TC. This signifies the enhancement of the long-range ferroelectric order due to the alignment of polar nanoregions (PNRs) along the field direction. After poling the crystal with a high electric field for 60 min above TC, the alignment of all PNRs along the field direction was observed. By decreasing the poling time, LA mode splitting was observed below TC owing to the back switching of PNRs. In a field-dependent measurement below TC, a mixed state consisting of macro- and nanodomains persisted up to a very high electric field because of the incomplete switching of nanodomains due to the interaction among PNRs.

Section: Introductionmentioning

confidence: 99%

Electric field effect on polar nanoregions of uniaxial ferroelectric Sr_xBa₁₋_xNb₂O₆with weak random fields studied by Brillouin scattering

Dec

Kleemann

et al. 2018

Jpn. J. Appl. Phys.

“…By the low temperature acoustic emission, a field induced orthorhombic phase is observed within the modulated incommensurate tetragonal structure of SBN75 47 . The crystal structures of SBN and other REFs with TTB structure such as Ca x Ba 1− x Nb 2 O 6 (CBN) have been reinvestigated using an automated electron diffraction tomography method with beam precession to confirm the tetragonal symmetry with space group P 4 bm at room temperature 48 . The appearance of quasi-static precursor polar regions near T C in the paraelectric phase has been observed by piezoresponse force microscopy (PFM) 41 and Raman scattering 49 .…”

Section: Introductionmentioning

confidence: 99%

Electric field and aging effects of uniaxial ferroelectrics Sr x Ba1−x Nb2O6 probed by Brillouin scattering

Helal

Paszkowski

et al. 2017

Sci Rep

Self Cite

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 (T C). 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 T C 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 T C. 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 T C was attributed to the complete switching of nanodomain to macrodomain state owing to the lack of interaction among PNRs. After isothermal aging below T C, the noticeable increase of LA velocity was observed. It was unaffected by cyclic temperature measurements up to T C, and recovered to initial state outside of a narrow temperature range above and below aging temperature.

“…38,49) In order to confirm the room-temperature tetragonal symmetry of SBN and CBN, their crystal structures have been reinvestigated by automated electron diffraction tomography with beam precession. 50) The stability of ferroelectric domain patterns induced by local electric fields in pure and Ce-doped SBN61 and SBN75 has been studied by PFM. 51) Recently, the Brillouin scattering measurements of uniaxial relaxor CBN30 single crystals have been performed under external dc electric fields.…”

Section: Introductionmentioning

confidence: 99%

Electric field effect on elastic properties of uniaxial relaxor Sr_xBa₁₋_xNb₂O₆single crystals with strong random fields

Helal

Dec

et al. 2017

Jpn. J. Appl. Phys.

The elastic properties of uniaxial relaxor SrxBa1−xNb2O6 (x = 0.70, SBN70) single crystals with strong random fields (RFs) were studied by Brillouin scattering spectroscopy as functions of temperature and external electric field along the [001] direction. A remarkable diffuseness of a ferroelectric phase transition was observed both on zero field heating and zero field cooling. The analysis of elastic anomaly shows the stretched critical slowing down of polar nanoregions (PNRs). Under 3.0 kV/cm, a complete alignment of nanodomains and an enhancement of the long-range ferroelectric order were observed below the Curie temperature TC = 23 °C. The alignment of quasistatic PNRs above TC was also observed under a sufficiently strong electric field. In a field-dependent measurement, a mixed state consisting of field-induced macrodomains and nanodomains caused by RFs was observed at 3.4 kV/cm. This mixed state persisted up to 9.0 kV/cm due to the incomplete switching of nanodomains to the macro/single domain state.