Phase transitions and twinning in NaNbO3 crystals

Revealing the mechanism of electric-field-induced phase transition in antiferroelectric NaNbO3 by in situ high-energy x-ray diffraction

“…The primitive cells oriented in the <110> direction exhibit a tensile stress in the direction parallel to the field and a compressive stress in the direction perpendicular to the field. The presence and the previously-predicted first order nature of the transition 6 were additionally confirmed by detecting slight cooling of the sample between 6 and 8 kV/mm, indicative of the absorbed latent heat (Figure S3). Due to the first order nature of this transition, both phases coexist over a certain period (certain E-field range).…”

“…The fieldinduced transformation of the non-polar P phase (AFE, orthorhombic Pbcm) 24 into the polar Q phase (FE, orthorhombic P21ma) 25 is accompanied by a large longitudinal strain of 0.64 %, drop in the permittivity, disappearance of the translational AFE domain structure, and changes of the local Na environment 5 . The transition was previously suggested to be of the first order nature 6 .…”

“…Decoupling of the field induced phase transition and polarization switching is related to the randomly-oriented grains and mechanical stress present at the phase boundary.Antiferroelectric materials are characterized by a phase transition from an antiferroelectric (AFE) to a ferroelectric (FE) state induced by the application of an external electric field. This transition is often accompanied by the appearance of double polarization hysteresis loops, depending on whether the transition is reversible 1-4 or irreversible 5,6 . Reversible AFE-FE transitions enable potential application of AFE materials in a wide range of devices, including high energy density capacitors 7-10 , non-volatile random access memory 11 , and electrocaloric refrigerators 12,13 .…”

“…materials, double polarization loops were only verified in certain single crystals 6,19 . Instead, the electric-field-induced phase transition was reported to be irreversible 5,20 , resulting in characteristic FE polarization loops after the first electric field cycle.…”

Domain morphology of newly designed lead‐free antiferroelectric NaNbO3‐SrSnO3 ceramics

“…28 In the 1980s, it was concluded that only 90° and 60° domains were allowed in orthorhombic NN by the crystallographic symmetry. 21,30 In the late 1980s, (transmission) electron microscopy has started to play an important role in visualizing the 90° and 60° domains in both NN single crystals and polycrystalline ceramics. [31][32][33] Since the 21st century, the rapid development of transmission electron microscopy (TEM) has enabled its wide application in the investigation of the domain structures.…”