Polarization-Based Adjustable Memory Behavior in Relaxor Ferroelectrics

Abstract

The irreversible decay of the spontaneous polarization above the phase-transition temperature is a limiting factor in any application of ferroelectric crystals. Here we show that electric fields applied at high temperatures induce a preferred direction in the crystal which is stable even after repeated heating and cooling through the phase transition. This preference in direction leads to a reorientation of domains in the ferroelectric phase. We use pyroelectric measurements to show that the directional preference originates from internal charge carriers interacting with domain walls.

High-temperature poling of ferroelectrics

“…An additional effect that might come into play in this case is the migration of mobile charge carriers, activated by the high temperature, which compensate for the depolarizing fields at domain walls and stabilize the domain structure. A similar effect has been observed when poling ferroelectric single crystals at high temperatures 28,29 or when high fields are applied to a PZT ceramic at RT for long times. 14 It is possible that due to this compensation for depolarizing fields, a stable macroscopic polarization can be achieved at high temperatures even for low poling fields, eliminating the field threshold observed in our experiments.…”

Aging and slow dynamics inSrxBa1−xNb2O6

“…͑Similar results were found for SBN: La, except that the anomalous self-poling in zero field was negligible.͒ The most striking feature is that a substantial polarization tail persists above T P . While a roughly similar tail has been found in similar measurements on Ce-doped SBN, 22 the interpretation focused on possible critical behavior below T P . The high-T polarization tail found here shows a distinct feature, indicating that some distinct process is present.…”

Intensity dependent properties of photo-induced light scattering in ferroelectric Sr0.61Ba0.39Nb2O6:Ce

“…This field remains in the crystal even after the illumination is finished, partially hindering a further spatial domain reversal with the external fields. At the same time, possibly because of the increased mobility of the local charge centres at high temperatures [26], the internal fields cannot be compensated completely by photoelectrons. Therefore, domain walls still can be pinned by the internal fields.…”

“…Electric poling of SBN by the field cooling technique (FC poling), i.e. a high external field is applied in the paraelectric phase and remains on the sample until it is cooled down to the ferroelectric phase, imposes the same spatial order in ferroelectric domains and in the distribution of local internal fields in the bulk [25,26]. This is because, at high temperatures, the mobility of local charge centres is rather high, and they arrange according to the external field.…”