Field dependent elastic anomaly in uniaxial tungsten bronze relaxors

Abstract

The electric field effects on the elastic properties of uniaxial Ca x Ba1− x Nb2O6 (x = 0.30, CBN30) single crystals were investigated using broadband Brillouin scattering spectroscopy as functions of temperature and electric field. Remarkable thermal hysteresis was observed between zero field heating and zero field cooling processes. A stretching index β = 2.05 indicates the stretched critical slowing down of polar nanoregions (PNRs). The effect of electric field along [001] direction was clearly observed. Under 1.0 kV/cm field, the alignment of nanodomains and enhancement of the long-range ferroelectric order were observed in the ferroelectric phase. In the field dependent measurement, a mixed state consisting of macrodomains induced by the electric field and nanodomains caused by the random fields was observed at 3.0 kV/cm. The mixed state persists up to 13 kV/cm because of the incomplete switching of the nanodomains to the macrodomains state. A very strong memory effect was also observed.

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

“…5) was observed due to a complete switching of the nanodomain state induced by the RFs into the macrodomain/single domain state induced by the external electric field. A similar acoustic anomaly was observed in a CBN30 single crystal at a low temperature region 53 , while the anomaly near T C was not observed. Presumably the applied field was not sufficient for overcoming the RFs and switching the nanodomains.…”

“…The field induced single domain state and spontaneous back switching are observed in SBN61 39, 45 . Recently, a CBN30 single crystal has been studied by Brillouin scattering under dc electric field 53 . In the ferroelectric phase, an incomplete alignment of nanodomains and enhancement of the long-range ferroelectric order are observed.…”

Electric field effect on polar nanoregions of uniaxial ferroelectric SrxBa1−xNb2O6with weak random fields studied by Brillouin scattering

“…Figure 2 shows the temperature dependence of the V LA of a SBN40 single crystal on ZFC after poling the crystal with 5.0 kV=cm at 160°C for 60 min (pink curve) and 1 min (red and orange curves), respectively. 53) After poling the crystal with 5.0 kV=cm for 60 min at 160°C, the V LA of the crystal during ZFC (pink curve) was comparable to that on FC with 0.5 kV=cm (olive curve) as shown in Fig. 2.…”

“…A similar behavior of V LA was also observed in CBN30 and SBN70 relaxors. 44,45) The mixed state persisted up to 13.0 kV=cm owing to the incomplete switching of the nanodomains into the macro= single-domain state. Below T C , PNRs are strongly correlated with each other; hence, the switching of nanodomains by the external electric field becomes interrupted.…”

“…46) Figure 1 shows the temperature dependence of the V LA of a SBN40 single crystal on ZFC and field cooling (FC) under 0.5, 1.0, and 3.0 kV=cm electric fields along the [001] direction. 53) The external electric field overcomes the quenched RFs and aligns PNRs along the field direction in the paraelectric phase above T C . Therefore, upon FC, PNRs are frozen with the preferred orientation induced by the external electric field.…”