nan Aftabuzzaman

Electric field effect of relaxor ferroelectric (1 − x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 crystals near morphotropic phase boundary composition probed by Brillouin scattering

The relaxor ferroelectric (1 − x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (x = 0.30, PMN–30PT) single crystal was studied under the zero field and the externally applied dc electric field by using micro-Brillouin scattering and dielectric spectroscopies over a wide temperature range of 303–773 K. The noticeable thermal hysteresis of longitudinal acoustic (LA) shift (νB) was observed between zero field heating and zero field cooling processes. Under the electric field of 0.5 kV/cm along the [001] axis, the LA mode splitting was observed in νB due to the coexistence of ferroelectric macrodomain and nanodomain states caused by the random field, and in dielectric measurements the monoclinic (M) and tetragonal phases were appeared between rhombohedral and cubic phases. The LA mode splitting and M phase disappeared under the field of 1.0 kV/cm. The electric field dependence of LA velocity was studied at 304 K. The critical end point of the PMN–30PT single crystal was investigated.

Temperature evolution of central peaks and effect of electric field in relaxor ferroelectric 0.83Pb(Mg1/3Nb2/3)O3–0.17PbTiO3 single crystals

Relaxor ferroelectric 0.83Pb(Mg1/3Nb2/3)O3–0.17PbTiO3 (PMN–17PT) single crystals were studied by Brillouin scattering to investigate the role of polar nanoregions (PNRs) with intermediate random fields (RFs). Upon cooling, the central peak began to appear at the Burns temperature (T B) of ~600 K, indicating the existence of polarization relaxations induced by PNRs. The fitting performed using the equation of stretched slowing down at the inverse relaxation time revealed that the slowing down of PNRs was suppressed in PMN–17PT compared with that in PMN–56PT owing to the increase in the strength of RFs. At room temperature, the splitting of the longitudinal acoustic mode at 1.6 kV/cm was observed owing to the coexistence of the macrodomain formed by the external electric field along the [100] axis and the nanodomains formed by RFs. The appearance of the transverse acoustic mode at 3.2 kV/cm indicates the field-induced rhombohedral-to-tetragonal phase.

Electric field effect on elastic properties of uniaxial relaxor SrxBa1−xNb2O6 single crystals with strong random fields

The elastic properties of uniaxial relaxor Sr x Ba1− x Nb2O6 (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 T C = 23 °C. The alignment of quasistatic PNRs above T C 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.

Memory effects of relaxor ferroelectric 0.70Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 single crystals studied by dielectric spectroscopy

ABSTRACT Dielectric properties of relaror ferroelectric 0.70Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PMN-30PT) single crystals were studied under the external electric field in a wide temperature range. After removing the field, dielectric spectra measured on zero field heating were different from initial condition, and this fact indicates the presence of a strong memory effect in PMN-30PT crystals. To clarify the correlation between this memory effect and polar nanoregions, dielectric spectra measured under the constant field were studied after short-circuiting the electrodes of a poled crystal at different high temperature regions. The process of removing the memory effect was clarified, which is extremely necessary for device application.