共查询到20条相似文献,搜索用时 31 毫秒
1.
A model of ferroelastic domain walls consisting of matching interlayers of crystal lattices is proposed. The dependences of the parameters of the interlayers and of the parameters of the equations for W′ and W domain walls on the crystal lattice parameters of the ferroelastic phase in Pb3(PO4)2 are determined. The problem concerning the number of possible orientational states and their interaction in a polydomain crystal is considered. 相似文献
2.
H. Schmid 《Phase Transitions》2013,86(1-4):205-214
A short overview is given on recent polarized light microscopy studies of the orthorhombic ferroelastic domains and domain structures of YBa2Cu3O7-x . The optical characteristics of large domains and lamellar domains with a high density of twin walls are pointed out, both for reflected and transmitted light. The polarizing microscope has allowed to observe the ferroelastic detwinning in situ and to determine the activation energy of the ferroelastic wall movements. The question of a potential ferroelectric phase transition is also discussed. 相似文献
3.
E. Wiesendanger 《Czechoslovak Journal of Physics》1973,23(1):91-99
Domain configurations in large KNbO3 single crystals grown by a top seeded flux growth technique are studied by optical methods and etching techniques. The orientation of observed domain walls is consistent with the principles of mechanical compatibility and electrical neutrality. Experimental evidence for the existence of a new type of ferroelectric domain wall (S-wall) is presented. Miller indices of such walls are irrational and depend on spontaneous strain tensor coefficients. The preparation of large single domain crystals (up to 1/3 cm3) is described. Assessment of crystal perfection by x-ray topographic and interference methods reveals a very small mosaic spread (one minute of arc) and a good optical homogeneity. 相似文献
4.
5.
J. Přívratská 《Phase Transitions》2013,86(5):338-342
Orientation of compatible domain walls and magnitude of disorientation angle of a ferroelastic domain twin resulting from phase transition hexagonal to monoclinic phases is expressed in crystallographic unit-cell parameters of the low-symmetry phase. These two characteristics, the orientation of the compatible wall and the disorientation angle, depend on the spontaneous strain in two single-domain states R 1, R 2 from which the domain twin is formed. They have been determined for all classes of the compatible domain walls as a function of the strain-tensor components [A. Authier, International Tables for Crystallography, in Physical Properties of Crystals, Chapter 3.4, Vol. D, A. Authier, ed., Kluwer Academic Publishers, Dordrecht, 2003, pp. 449–505]. If relative changes of crystal lattice are small, then the second rank symmetrical strain tensor u can be calculated from the crystallographic unit-cell parameters before and after the deformation [J.L. Schlenker, G.V. Gibbs, and M.B. Boisen Jr, Strain-tensor components expressed in terms of lattice parameters, Acta. Cryst. A 34 (1978), pp. 52–54; L. Jian and C.M. Wayman, Domain boundary and domain switching in a ceramic rare-earth Orthoniobate LaNbO4 , J. Am. Ceram. Soc. 79 (1996), pp. 1642–1648]. An alternative approach expresses the disorientation angle and orientation of the compatible domain wall [J. P?ívratská, Disorientation angle expressed in terms of lattice parameters, Ferroelectrics 291 (2003), pp. 197–204] in terms of the crystallographic unit-cell parameters of the low-symmetry phase. 相似文献
6.
We present a theoretical investigation of elementary excitations in anisotropic antiferromagneticS=1 chains using the concept of domain walls in string (hidden) order. Domain walls are classified by the internal spin projectionS
dw
z
. We calculate energies and string correlation
0 functions of low lying excited states of the domain wall type in the Haldane phase and compare the results to those of numerical
computations. The boundaries of the Haldane phase are determined from the instability of these excitations with respect to
the ground state. The interaction between two domain walls is found to be proportional to the productS
dw
z
, S
dw
z
2, it is effectively repulsive 0140 for equal
spin projections. 相似文献
7.
Two methods are suggested for writing equations for domain walls in a coordinate system of the ferroelectric phase in ferroelastics and multiaxial ferroelectrics. The equations for domain walls in ferroelectric barium titanate and ferroelastic lead orthophosphate are derived. It is shown that suborientation states are possible in these crystals. The suggested methods make it possible to find the matrices of the transformation from the coordinate system of the paraelectric phase to a coordinate system of the ferroelectric phase for each orientation state. 相似文献
8.
Ekhard K.H. Salje 《Phase Transitions》2013,86(1):2-14
Some domain boundaries contain functionalities which do not exist in the bulk. Typical examples are (super-) conducting twin walls in WO3, highly conducting walls in BiFeO3 and in structural interfaces between SrTiO3 and LaAlO3, and ferroelectric walls in CaTiO3. The emerging field of ‘Domain Boundary Engineering’ endeavors to generate such functional interfaces in a multitude of materials for applications in device materials. Some of the recent successes are reviewed together with suggestions for further research. 相似文献
9.
Domain structure of BiFeO3 ceramics has been investigated using a combination of piezoresponse force microscopy (PFM) and Raman scattering techniques. Both methods demonstrate the presence of ferroelastic domains, separated by almost parallel planar domain walls, as well as the presence of large homogeneous single ferroelastic domain regions. In addition to highly resolved domain pattern obtained by PFM, small frequency shifts of the Raman-active modes give us complementary information about the angle φ between the surface normal and the rhombohedral axis of the BiFeO3 crystal for any measured position at the surface of the sample. 相似文献
10.
Ulrich Bismayer Dagmar Mathes Mois Aroyo Dirk Bosbach Andrew Putnis Gustaaf Van Tendeloo 《Phase Transitions》2013,86(3):243-270
Ferroelastic domain patterns in lead phosphate-type crystals depend on their chemical composition. The intersection of ferroelastic W domain walls with the (100) surface of lead phosphate-arsenate mixed crystals has been imaged using tapping mode atomic force microscopy. Dilution of the strain leads to characteristic surface deformations which deviate from those in pure lead phosphate. In highly twinned lead phosphate-arsenate X-ray diffraction was used to show renormalization effects and scattering phenomena stemming from the twin walls. Raman-active hard modes show wall-related profile changes and low-frequency tails. Symmetry mode analysis is used to describe the displacive modes characterizing the structural distortion in lead phosphate-arsenate for the sequence K m → P21/c. 相似文献
11.
J. Fousek 《Czechoslovak Journal of Physics》1971,21(9):955-968
A previously developed method makes it possible to determine the orientations of domain walls in ferroelectrics which are permissible under the condition that neighbouring domains must be mechanically compatible. In this paper, the method has been applied to all 88 ferroelectric species in which the polarization is the parameter of the transition. Types of permissible walls and their orientations are listed in form of tables. Cases where no walls fulfil the compatibility conditions are shown. 相似文献
12.
The existence of wall or boundary free energies is discussed generally and analyzed explicitly for general lattice systems with scalar (real-valued) spin variables. For systems with ferromagnetic (positive) spin interaction potentials,K, in the bulk andW, for the walls, correlation inequalities and appropriate stability and tempering conditions are used to establish the existence and uniqueness of the limiting free energy per unit area,f
x(K,W), of an infinite planar wall. 相似文献
13.
J. C. Toledano 《Phase Transitions》2013,86(1-4):1-2
This review contains up-to-date information about experimental and theoretical investigations of phase transitions and specific features of properties of mixed crystals involving the incipient ferroelectric KTaO3 with the off-center Li+, Nb5+, Na+ impurities. Main attention is paid to the results of the study of the mixed systems by radiospectroscopy methods (ESR and NMR). Theoretical criteria and experimental evidence of ferroelectric and ferroelastic phase transitions as well as of dipole and quadrupolar glass states induced by the off-center impurities are discussed. It is shown that at high enough concentrations of the off-center impurities phases with long-range order appear, but at low concentrations dipole glass states occur. At intermediate concentrations of the off-center impurities new phases appear in which the coexistence of long-range properties and those of dipole glasses is possible. These phases could be named ferroelectric or ferroelastic glasses to stress their similarity with the ferroglass phases which were discovered earlier in mixed magnetic systems. The usefulness of radiospectroscopy methods for the study of phase transitions induced by off-center impurities in mixed systems, which can be considered as model disordered systems, is underlined. In conclusion, some questions on the physics of phase transitions in disordered systems which should be solved in the future are discussed. 相似文献
14.
Using transmission electron microscopy, in-situ changes in ferroelastic domains in 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals were observed at 60 to -163°C. At -163°C, the microscopic tweed morphology of the ferroelastic domains rotated by 90°, and certain orientation changes in the mesoscopic sawtooth domains took place. At this temperature, the ferroelastic domains became coarsened and certain S-shaped mesoscopic domains were reshaped. The disappearance and/or changes in the orientations of both the sawtooth and the ferroelastic domains were reversible upon return to room temperature. On heating to 60°C, both the mesoscopic sawtooth and the microscopic tweed domains were stable below 53°C. Above 53°C, the mesoscopic walls disappeared and the contrast of the tweed domains became blurred. Upon return to room temperature from 60°C, the mesoscopic domain patterns could not be retrieved, indicating that the transformation was irreversible. The morphology of the tweeds at this temperature indicated a structural transition from a two-variant domain state to a multivariant state, eliminating mesoscopic boundaries. 相似文献
15.
Distinctive features of domain formation in ferroelectric crystals are discussed theoretically for the example of ferroelectric
BaTiO3, taking into account ferroid properties of higher order. Inclusion of ferroid properties makes it possible to refine the
details of the domain formation, and in particular to explain the possible existence of charged domain walls in ferroelectric
crystals.
Fiz. Tverd. Tela (St. Petersburg) 39, 1634–1635 (September 1997) 相似文献
16.
The effective thickness of ferroelastic twin-walls (W-walls) in Pb3(PO4)2 at room temperature (≈ 0.7 T c ) was determined by X-ray diffraction. The diffraction profiles were analysed using a wall profile e=eotanh x/w where W is the effective wall thickness including the effects of wall bending and surface relaxations. The experimental value W is around 10 unit cells which is larger than expected from standard renormalization arguments. The limitations of such experimental studies are discussed. 相似文献
17.
We present a theoretical investigation of elementary excitations in anisotropic antiferromagneticS=1 chains using the concept of domain walls in string (hidden) order. Domain walls are classified by the internal spin projectionS dw z . We calculate energies and string correlation functions of low lying excited states of the domain wall type in the Haldane phase and compare the results to those of numerical computations. The boundaries of the Haldane phase are determined from the instability of these excitations with respect to the ground state. The interaction between two domain walls is found to be proportional to the productS dw z , S dw z 2, it is effectively repulsive for equal spin projections. 相似文献
18.
《Physics letters. A》2020,384(14):126279
The structures, energies, spontaneous polarized properties and charge densities of 180° domain walls with Mn doping at different lattice positions were investigated in ferroelectric PbTiO3 (PT) using the first-principles calculations. The results show that Mn ion prefers to enter the bulk region rather than the domain wall in terms of energy minimization whether it substitutes for an A-site Pb ion or a B-site Ti ion of PT. In addition the domain wall energy has a minimum value of 124.52 mJ/m2 when Mn ion substitutes for Pb ion in the bulk region. And the spontaneous polarization along z axis increasing and the charge density in the domain wall region reducing could be the essential reasons for improving PT's performance after Mn doping at A site. 相似文献
19.
A. L. Sukstanskii 《Zeitschrift für Physik B Condensed Matter》1992,86(1):69-75
Domain walls in the four-sublattice antiferromagnet La2CuO4 are considered. The spin waves spectrum on the single domain wall is studied. The stability of the walls and the intrawalls phase transitions are analysed. 相似文献
20.
Hard mode Raman spectroscopy and its application to ferroelastic and ferroelectric phase transitions
U. Bismayer 《Phase Transitions》2013,86(4):211-267
The application of Raman spectroscopy for the investigation of phase transitions focused traditionally on the observation of soft modes in displacive systems. The present furthergoing study on displacive and order-disorder systems is based on the observation of systematic changes of the scattering profiles of hard modes during the phase transition. It reveals the temperature evolution of the order parameters, the role of order-parameter fluctuations and phonon density of states effects in model systems like improper ferroelastic Pb3(P1-x As x O4)2, lead diluted ferroelastic (Pb1-x Ba x )3(PO4)2, pure ferroelastic As2O5 and the relaxor ferroelectric Pb(Sc0.5Ta0.5)O3. Allied with supplementary experimental techniques hard-mode Raman spectroscopy (HMRS) is an ideal method for the investigation of order-parameter coupling effects and the characterization of structural phase transitions. 相似文献