Showing papers on "Ferroelasticity published in 1985"
31 citations
TL;DR: The phase transition of the phenothiazine crystal was studied by the Raman spectroscopy in the lattice region, differential scanning calorimetry, and the inspection under a polarizing microscope as discussed by the authors.
12 citations
TL;DR: In this article, a model based on a Landau development of the free energy is presented to account for the mechanism of the isotranslation phase transition from P4/mnc space group to P21/n, occurring in chiolite Na5Al3F14 at Tc=150K.
Abstract: For pt.I see ibid., vol.18, no.36, p.6555 (1985). A model, based on a Landau development of the free energy, is presented to account for the mechanism of the isotranslation phase transition from P4/mnc space group to P21/n, occurring in chiolite Na5Al3F14 at Tc=150K. Coupling between the Eg optical soft mode and the strain of the same symmetry is considered (pseudo-proper ferroelastic transition) and expressions are derived for the behaviour of the soft-mode frequencies and for that of the elastic constants c44 and c55. The model is consistent with the experimental results obtained for the optical soft-mode (in paper I); furthermore, there is evidence of a changeover in the transition regime at T0 approximately=120K. It is interpreted as the result of a predominant contribution in the order parameter due to the optical mode below T0, whereas in the vicinity of Tc, the predominant contribution is due to the strain.
4 citations
TL;DR: In this article, the elastic constants of polycrystalline Nb3Sn were determined as a function of temperature when the samples were submitted to uniaxial tensile stress.
Abstract: The elastic constants of polycrystalline Nb3Sn were determined as a function of temperature when the samples were submitted to uniaxial tensile stress. The Young’s (E) and shear (G) moduli were obtained from an ultrasonic pulse transmission technique in the range 4–300 K. Their behavior with temperature and applied stress is discussed in terms of the martensitic phase transformation occurring at ∼43 K and the ferroelastic character of the tetragonal phase (T <43 K). Uniaxial tensile stress is found to stiffen the moduli at all temperatures by stabilizing the crystal structure and by progressively eliminating the domains in the tetragonal phase.
3 citations
TL;DR: In this paper, it was shown that neodymium pentaphosphate can be made to twin under the influence of mechanical stress, which can become the basis of novel optical and acoustic devices.
Abstract: Crystals that can be made to twin under the influence of mechanical stress have been known for some time; neodymium pentaphosphate may become the basis of novel optical and acoustic devices.
1 citations
TL;DR: In this paper, a theoretical model of the 61.5 K transition in Nickel-iodine boracite is presented, based on a six-dimensional irreducible core presentation of the F3cl' paramagnetic group, which shows that the simultaenous onset of the magnetic ferroelectric and ferroelastic properties can be foreseen from the symmetry of the transition order parameter.
Abstract: A theoretical model of the 61.5 K transition in Nickel-iodine boracite is presented. Based on a six-dimensional irreducible corepresentation of the F3cl' paramagnetic group, it shows, within the framework of the Landau theory, that the simultaenous onset of the magnetic ferroelectric and ferroelastic properties can be foreseen from the symmetry of the transition order-parameter. The primary order-parameter is identified as a latent antiferromagnetic ordering. The weak magnetization, polarization and strain components originate in an improper coupling of these quantities with the antiferromagnetic sublattice magnetization. The corresponding magnetic, dielectric, elastic and magnetoelectric anomalies, are briefly discussed.
1 citations