Phase fronts at the NaNbO<sub>3</sub>P‐⇌ NaNbO<sub>3</sub> R phase transition

Dec, J.

doi:10.1002/crat.2170190102

Cited by 7 publications

(2 citation statements)

References 13 publications

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“…In Fig. 1, P T F is geometrically analogous to that observed by Dec [17] with an optical microscopy. The region in the left bottom side of the P T F in Fig.…”

Section: The P-r Phase Transition I S Of First Order the R-s One Is supporting

confidence: 75%

In situ TEM studies of para—ferro phase transitions in NaNbO3

Chen

Ding

1988

Phys. Stat. Sol. (a)

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It is found from TEM observations in NaNbO3 crystals that the phase transition series from the P phase is P—R1—R2—S and that one, related to the Q phase is Q—Q1—Q2—S. It is shown that the R phase is composed of two subphases R1 and R2. The main difference between R1 and R2 is that the η values corresponding to these two phases in the superlattice spots [1/2, 1/2 ± η1/2, 0]* are 1/4 and 1/6, respectively. But the η values in the superlattice spots [1/2 ± η 1/2, 0]* corresponding to the Q1 and Q2 phases are 0 and 1/3, respectively. The main soft mode of the transition from phase S to R2 is determined as the zone boundary transverse optical mode Σ2 with wave vector q equal to [1/2, ξ, 0]*. The appearance of a superlattice spot at [1/2, 1/2, 0]* shows that the mode characterizing the tilt of octahedra is also softened due to mode—mode coupling.

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“…In Fig. 1, P T F is geometrically analogous to that observed by Dec [17] with an optical microscopy. The region in the left bottom side of the P T F in Fig.…”

Section: The P-r Phase Transition I S Of First Order the R-s One Is supporting

confidence: 75%

In situ TEM studies of para—ferro phase transitions in NaNbO3

Chen

Ding

1988

Phys. Stat. Sol. (a)

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“…It was observed in various other transformations, e.g. in NHaNO3 (Geguzin, Kruzhanov & Starukina, 1985), BaTiO3 (Burfoot & Parker, 1966), PbTiO3 (Dec, 1986(Dec, , 1988Fesenko, Sindeyev, Gavrilyachenko & Semenech, 1975;Yufatova, Sindeyev, Gavrilyachenko & Fesenko, 1980), NaNbO3 (Dec, 1984(Dec, , 1986 and [N(CH3)4]2ZnCI4 (Jennissen, 1989). In all these cases, the phase boundaries exhibit favourite low-energy directions.…”

Section: Movement Of the Phase Boundarymentioning

confidence: 98%

An X-ray Topographic Study of the Paraelectric-to-Ferroelectric Phase Transformation in Nearly Perfect Single Crystals of Ammonium Sulfate

Bhat¹,

Klapper²

1995

J Appl Cryst

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The basic defect structure of solution‐grown single crystals of ammonium sulfate and changes to it as it undergoes a paraelectric to ferroelectric phase transition at 223 K are investigated using conventional Lang and white‐synchrotron‐radiation X‐ray topography. Topographs of thick (ca 1 mm) plates reveal the existence of lattice strain prior to transformation. The shape of the phase boundary is revealed from studies of thinner plates (ca 0.3 mm). These show sharply defined zigzag‐shaped boundaries between the paraelectric and the ferroelectric phases in plates cut parallel to (010) and (001). Cracks and dislocation loops (Burgers vector [001]) generated by plastic deformation are found to originate from the apices of the zigzag boundaries. No distinct phase boundaries were observed in (100) plates. The preferred (energetically favoured) orientations (i.e. the zigzag segments) of the phase boundaries in (010) and (001) as well as their blurred appearance in (100) plates are explained by the specific properties of the strain tensor associated with the transition. Ferroelectric domains have also been detected by the faint dynamical X‐ray contrast of their boundaries (180° walls).

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