Showing papers on "Ferroelasticity published in 1994"
TL;DR: In this paper, the authors reviewed the domain aspects of multi-ferroics, i.e. of materials, in which two or all three properties of the properties "ferroelectricity" and "ferromagnetism" occur simultaneously in the same phase, and in which the magnetic point group has been reliably established by magnetoelectric, optical, dielectric and related studies on single crystals and single domains.
Abstract: Domain aspects of multi-ferroics are reviewed, i.e. of materials, in which two or all three of the properties ‘ferroelectricity.’ ‘ferromagnetism’ and ‘ferroelasticity’ occur simultaneously in the same phase, and in which the magnetic point group has been reliably established by magnetoelectric, optical, dielectric, magnetic and related studies on single crystals and single domains. Nearly only members of the boracite crystal family are concerned, whereas for the perovskite family and other classes of material there is great paucity of data on single crystals. Polarized light microscopy is shown to be an indispensable tool for the study of multi-ferroics, in particular when ferroelasticity is involved. Potential multi-ferroic magnetoelectrics, so far only known in ceramic form, are excluded from the survey.
1,154 citations
TL;DR: In this article, the specific relationship of five highly structure dependent physical properties, namely piezoelectricity, pyroelectricity, ferro-electricity and optical activity, to atomic arrangement are developed.
Abstract: Crystallography provides a major approach toward reaching an understanding of the relationship between crystal structure and material physical properties The specific relationships of five highly structure dependent physical properties, namely piezoelectricity, pyroelectricity, ferroelectricity, ferroelasticity and optical activity, to atomic arrangement are developed in this Lead Article The major attributes of each property, together with the structural measurements required to establish the property–structure relationship, are introduced and illustrative results for each are given Predictive criteria that emphasize the insight leading to new property-structure relationships are presented as is an expanded experimental access to the crystallographic study of materials
58 citations
TL;DR: A review of experiments and theoretical descriptions for the order-disorder phase transition in MSCN (M = K, Rb, NH4, Tl) is given in this paper.
Abstract: A review of experiments and theoretical descriptions for the order-disorder phase transition in MSCN (M = K, Rb, NH4, Tl) is given. These crystals which have an appealing structure exhibit a phase transition from an orthorhombic low-temperature phase to a tetragonal high-temperature phase at elevated temperatures. Emphasis is placed on KSCN which was investigated intensively during the last few years. We present a summary of quite complementary measurements, of birefringence, elastic constants, diffuse neutron scattering and nuclear magnetic resonance and relate these results to earlier data in the literature. Distinct precursor effects which show up in diffuse neutron scattering preface this phase transition in both phases. These order parameter fluctuations are however limited; as a result of the first-order nature of the phase transition in KSCN. The phase transitions in RbSCN and TISCN are very close to a tricritical point. The dynamical behaviour of the phase transition in KSCN is rather slo...
21 citations
TL;DR: In this paper, specific heat and X-ray measurement in the single crystals of TlH 2 AsO 4 were carried out in a temperature range between 80 K and 400 K, and its domain structures were observed.
Abstract: Dielectric, specific heat and X-ray measurement in the single crystals of TlH 2 AsO 4 were carried out in a temperature range between 80 K and 400 K, and its domain structures were observed. It was found that TlH 2 AsO 4 is ferroelastic below 391 K ( T I ) with the spontaneous strain x 5S =4.2×10 -2 at 293 K. TlH 2 AsO 4 has two distinct domain structures at room temperature; one is the domain structure with the (100) and/or (001) domain boundaries which disappears above T I and the other is the structure with the (201) domain boundary which has no relation with the phase transition. The crystal belongs to a monoclinic system with the space group P 2 1 / a in the room temperature phase and an orthorhombic system with the space group Pcan above T I . It is suggested that the ferroelastic phase transition at T I may be caused by an instability of acoustic B 2g mode.
20 citations
TL;DR: In this article, the authors investigated the domain structure of the BiVO4 single crystal using the nuclear magnetic resonance (NMR) of 51V and by the electron paramagnetic resonance (EPR) of the Mn2+ ions contained in the crystal as an impurity.
Abstract: The domain structure of the ferroelastic BiVO4 single crystal has been investigated using the nuclear magnetic resonance (NMR) of 51V and by the electron paramagnetic resonance (EPR) of the Mn2+ ions contained in the crystal as an impurity. The 14 resonance lines of 51V (I=7/2) in a BiVO4 crystal with the twin domain were measured in the crystallographic a-b (or c-b) and c-a (or a-c) planes with an FT NMR spectrometer. Two sets of Mn2+ EPR signals were also obtained in the c-a plane. These two sets of NMR and EPR signals originate from the twin-domain structure. From these two sets of experimental data from 51V NMR and Mn2+ EPR, it is confirmed that the BiVO4 single crystal has the prominent (W-plane) domain wall reported previously. The investigated domain structure is found to be stable with time in contrast with a previous report by Baran et al. The previous model of the twinning mechanism derived from NMR and X-ray diffraction data has been improved by employing the EPR results. The observed W plane of the domain wall in BiVO4 can be explained by the ferroelastic species 4/mmm F 2/m instead of 4/m F 2/m.
20 citations
18 citations
16 citations
TL;DR: In this paper, synthetic end-member strontium feldspar (SrAI2Si2Os) has been studied in a diamond-anvil cell at elevated pressures up to 10.3 GPa using energy-dispersive X-ray powder diffraction.
Abstract: Synthetic end-member strontium feldspar (SrAI2Si2Os) has been studied in a diamond-anvil cell at elevated pressures up to 10.3 GPa using energy-dispersive X-ray powder diffraction. Cell parameters have been refined between ambient pressure and 6 GPa. SrA12Si2Os undergoes a ferroelastic phase transition from the ambient pressure monoclinic space group 12/c to the high-pressure triclinic space group/1 at 3.2 ___ 0.4 GPa. The transition appears to be first-order and the ferroelastic and co-elastic components of the spontaneous strain tensor have been calculated.
15 citations
TL;DR: In this paper, X-ray diffraction studies of tetragonal zirconia polycrystals were conducted and the critical coercive stress was determined to be 1.65 ± 0.03 GPa.
Abstract: Neutron diffraction studies of tetragonal zirconia polycrystals subjected to various applied uniaxial stresses indicate that a ferroelastic crystalline transformation occurs within the bulk of the material. The critical coercive stress is determined to be 1.65 ± 0.03 GPa. The results agree well with previous reports concerning the ferroelasticity of tetragonal zirconia, but they are the first direct evidence indicating that the anomalies observed using the first X-ray diffraction studies originate from the bulk of the ceramic and not solely from the surface. The preferred orientation observed in the tetragonal crystallites was measured as a function of applied uniaxial stress and interpreted via a resolved stress criterion. It is believed that the ferroelastic transformation can act as an energy-absorbing mechanism and hence toughen zirconia or ceramics containing dispersed zirconia.
14 citations
TL;DR: In this paper, the compatibility conditions of elasticity theory are applied to the calculation of strain fluctuations in ferroelastic materials, and the authors consider a transition with an acoustic phonon mode instability and an order-disorder transition with striction in the framework of Landau-Ginzburg functional.
Abstract: The compatibility conditions of elasticity theory are applied to the calculation of strain fluctuations in ferroelastic materials. A ferroelastic transition with an acoustic phonon mode instability and an order-disorder transition with striction are considered in the framework of the Landau-Ginzburg functional. Anisotropy of strain correlation functions and their critical behaviour in the symmetric phase near the transition point are analysed and compared with the results of the Ornstein-Zernike theory of fluctuations. Characteristic shape of the correlation functions (“butterflies”) are predicted.
12 citations
TL;DR: In this article, single crystals of Mn 3 B 7 O 13 Br (MnBr) boracite were studied between 300 and 550 K by means of thermal, dielectric, pyroelectric and ferroelectric characterization, under simultaneous visual control of the Ferroelectric/ferroelastic domain state of the samples.
TL;DR: In this paper, the ferroelastic domain walls are found to vanish and reappear with characteristics of a classical second-order transition on topographs on cycling the sample between room temperature and above the transition temperature.
Abstract: In situ observation of the ferroelastic phase transition in Er‐doped lanthanum pentaphosphate has been carried out by real time white‐beam synchrotron radiation x‐ray topography. The ferroelastic domain walls are found to vanish and reappear with characteristics of a classical second‐order transition on topographs on cycling the sample between room temperature and above the transition temperature. However, fluctuations of the number of domain walls with temperature approaching the Curie point are revealed for the first time and shown to be reversible. Discussions on these interesting phenomena are presented.
TL;DR: The results of a detailed TEM and group theoretical study of α-PbO and its low-temperature, improper ferroelastic phase transition are reported in this paper.
TL;DR: In this article, the role of second-order structural phase transitions and the softening of Raman active modes in proper ferroelasticity was considered. But the emphasis was not on the softness of the active modes.
Abstract: Mechanisms of second-order structural phase transitions and the softening of Raman - active modes are considered with the emphasis to the role of the latter in proper ferroelasticity.
TL;DR: In this paper, the ferroelasticity of rare earth pentaphosphate, MP5O14 (M: La-Tb) belonging to the species mmmF2/m is studied by scanning tunneling microscope (STM), electron spin resonance (ESR) and X-ray diffraction.
Abstract: The ferroelasticity of rare earth pentaphosphate, MP5O14 (M: La-Tb) belonging to the species mmmF2/m is studied by scanning tunneling microscope (STM), electron spin resonance (ESR) and X-ray diffraction. The temperature dependence (from room temperature to 180°C) of ferroelastic domain structure and monoclinic β angle of EuP5O14 was obtained by STM and X-ray diffraction (ω scan technique). The spin Hamiltonian parameters of LaP5O14:Cr3+ at 150°C in the para phase obtained from the ESR spectra are gx= gy= gz=1.97, D = 0.45 cm-1 and E = 0.05 cm-1. The principal axes of one of the Cr3+ paramagnetic centers are given by the Eulerian angles =15°, θ=90° and ψ= 0°.
TL;DR: In this article, the lengths of the a-and c-axes undergo continuous change at the highest temperature phase transition as the β-angle increases from 90° below 365 K to 90° in tetragonal phase III.
Abstract: Pb 5 Al 3 F 19 undergoes three first-order phase transitions; on cooling from phase I (4/m) to phase II (2/m) at 365 K, from phase II to phase III (4/m) at 305 K, and from phase III to phase IV (4 mm) at 120 K. The lengths of the a- and c-axes undergo continuous change at the highest temperature phase transition as the β-angle increases from 90° below 365 K; no difference is detectable between the lengths of the a- and b-axes in monoclinic phase II, within an accuracy of 0.007 A. The β-angle temperature dependence follows a power law with exponent that does not differ significantly from 1/2. At the 305 K first-order phase transition, the β-angle abruptly changes from its maximum value of 90.41° in phase II to 90° in tetragonal phase III; the a- and c-axes, however, maintain their continuous change in length through this transition
TL;DR: In this paper, the influence of domain structure on the elastic and anelastic properties and the temperature of the phase transition into the superconducting phase has been observed in YBa2Cu3O7−δ ceramic samples.
Abstract: YBa2Cu3O7−δ ceramic samples are found to show ferroelastic domain switching in the temperature range from 85 K to 925 K. The influence of domain structure on the elastic and anelastic properties and the temperature of the phase transition into the superconducting phase has been observed.
TL;DR: Growth and mechanical twinning in tetragonal KSCN and related crystals is treated as a normal domain structure resulting from a (improper) ferroelastic transition from a real or hypothetical cubic phase as discussed by the authors.
Abstract: Growth and mechanical twinning in tetragonal KSCN and related crystals is treated as a normal domain structure resulting from a (improper) ferroelastic transition from a (real or hypothetical) cubic phase. Some experimental data on the twinning are completed by a discussion of the crystal structure and an elementary (point-)group theoretical analysis of the domain structure.
TL;DR: In this paper, the phase transitions in [Mg(H2O)6]GeF6 were investigated with an Mn2+ EPR probe substituted for Mg2+ ions in the lattice.
Abstract: The phase transitions in [Mg(H2O)6]GeF6 are investigated with an Mn2+ EPR probe substituted for Mg2+ ions in the lattice. An axial symmetry phase with space group R 3 is observed above 403 K. The ferroelastic phase transition at 318 K is of first order and leads to monoclinic symmetry and to the development of a domain structure. In the intermediate phase the spectra exhibit anomalous changes of the lineshapes resulting from incommensurate modulation of the crystal field fine structure tensor. The results of EPR studies are interpreted both in terms of the plane-wave and multi-soliton models.
[Russian Text Ignored.]
TL;DR: In this article, the mechanism of the pressure-induced ferroelastic phase transition in rutil-like NiF is discussed within a simple lattice dynamical model and it is found that the phenomenon in question can be completely assigned to softening of single B1g mode and can be regarded as intrinsic property of the rutile family.
Abstract: The mechanism of the pressure-induced ferroelastic phase transition in rutil-like NiF is discussed within a simple lattice dynamical model2. It is found that the phenomenon in question can be completely assigned to softening of single B1g mode and can be regarded as intrinsic property of the rutile family.
TL;DR: In this paper, the temperature dependence of the thermal expansion in the vicinity of the incommensurate phase transition in [N(CH3)4]2ZnCl4-xBrx mixed crystals is found to deviate from that predicted within the Landau theory of phase transitions.
Abstract: The temperature dependence of the thermal expansion in the vicinity of the incommensurate phase transition in [N(CH3)4]2ZnCl4-xBrx mixed crystals is found to deviate from that predicted within the Landau theory of phase transitions. It is shown that the dominant contribution to this deviation in the immediate vicinity of Ti is due to the presence of defects. The character of the deviation is found to be in qualitative agreement with the theoretically predicted behaviour in the presence of random field type defects. In some compounds (x=0,2.4,2.9), the temperature dependence of the thermal expansion coefficient at T⩾Ti + 3 K can be described by a τα-dependence with α = 0.5. These values are in reasonable agreement with α = 0.5, corresponding to the fluctuation correction to the Landau theory. In solid solutions with a rather smeared paraelectric-incommensurate phase transition (x = 0.25,0.45), the value of this exponent is found to be between 0.8 and 0.9. This suggest that the contribution to the thermal expansion due to the defects in these crystals is, even quite far from the phase transition, comparable to the contribution due to order parameter fluctuations.
TL;DR: In this paper, X-ray diffraction studies of tetragonal zirconia polycrystals (TZP) subjected to a varying applied uniaxial stress indicates that a ferroelastic crystalline transformation occurs within the bulk of the material.
Abstract: Neutron diffraction studies of tetragonal zirconia polycrystals (TZP) subjected to a varying applied uniaxial stress indicates that a ferroelastic crystalline transformation occurs within the bulk of the material. The critical coercive stress was determined to be (1.65 {+-} 0.03) GPa for yttria stabilized TZP and (0.70 {+-} 0.05) GPa for ceria stabilized TZP. The results agree well with previous reports concerning the ferroelasticity of tetragonal zirconia, and provide direct evidence indicating that the anomalies observed using the first X-ray diffraction studies originate from the bulk of the ceramic and not solely from the surface. The preferred orientation observed in the tetragonal crystallites was measured as a function of applied uniaxial stress and interpreted via a resolved stress criterion. It is believed that the ferroelastic transformation can act as an energy absorbing mechanisms and hence toughen zirconia or ceramics containing dispersed zirconia.
TL;DR: In this article, the mechanism of the pressure-induced second-order proper ferroelastic phase transition (PFPT) in TeO2 is treated within a simple lattice dynamical model, which explains why this phenomenon arises without softening of any longwave optic phonon.
Abstract: The mechanism of the pressure-induced second-order proper ferroelastic phase transition (PFPT) in TeO2 is treated within a simple lattice dynamical model, which explains why this phenomenon arises without softening of any longwave optic phonon.