6 research outputs found
How do the grains slide in fine-grained zirconia polycrystals at high temperature?
Degradation of mechanical properties of zirconia polycrystals is hardly
discussed in terms of solution-precipitation grain-boundary sliding due to
experimental controversies over imaging of intergranular amorphous phases at
high and room temperatures. Here, the authors applied the techniques of
mechanical spectroscopy and transmission electron microscopy (TEM) to shed
light on the amorphization of grain interfaces at high temperature where the
interface-reaction determines the behaviour of fine-grained zirconia
polycrystals. They present mechanical spectroscopy results, which yield
evidences of an intergranular amorphous phase in silica doped and high-purity
zirconia at high temperature. Quenching of zirconia polycrystals reveals an
intergranular amorphous phase on TEM images at room temperature.Comment: 12 pages, 3 figure
Landau Theory of Domain Wall Magnetoelectricity
We calculate the exact analytical solution to the domain wall properties in a
multiferroic system with two order parameters that are coupled
bi-quadratically. This is then adapted to the case of a magnetoelectric
multiferroic material such as BiFeO3, with a view to examine critically whether
the domain walls can account for the enhancement of magnetization reported for
thin films fo this material, in view of the correlation between increasing
magnetization and increasing volume fraction of domain walls as films become
thinner. The present analysis can be generalized to describe a class of
magnetoelectric devices based upon domain walls rather than bulk properties.Comment: 9 pages, 4 figure
Effect of internal friction on transformation twin dynamics in SrxBa1-xSnO3 perovskite
The dynamics of transformation twins in SrxBa1-xSnO3 (x=0.6,0.8) perovskite
has been studied by dynamical mechanical analysis in three-point bend geometry.
This material undergoes phase transitions from orthorhombic to tetragonal and
cubic structures on heating. The mechanical loss signatures of the
transformation twins include relaxation and frequency-independent peaks in the
orthorhombic and tetragonal phases, with no observed energy dissipation in the
cubic phase. The macroscopic shape, orientation and relative displacements of
twin walls have been calculated from bending and anisotropy energies. The
mechanical loss angle and distribution of relaxation time are discussed in term
of bending modes of domain walls.Comment: 20 pages, 4 figure
The ferroelastic phase transition and non- 180° domain switching in La-modified lead zirconate titanate ferroelectric ceramics
The ferroelastic phase transition and shape memory effect in La-modified lead zirconate titanate ferroelectric ceramics are demonstrated directly through the temperature-dependent macroscopic recoverable strain measured in a three-point bending configuration. X-ray diffraction measurements reveal that non- 180° domain switching occurs in the mechanically poled sample in two different ways at the bottom and top of the sample which have been under tensile and compressive stresses, respectively. The calculated fraction of non- 180° switched domains in the poled sample increases nonlinearly with the applied force and shows a saturation trend, which is consistent with the nonlinear behavior of the remnant strain. This study confirms that the mechanical stress applied upon cooling ferroelectric ceramics from the paraelectric to the ferroelectric phase can easily activate ferroelastic domain switching and give rise to preferred domain orientation and consequent macroscopic remnant strain which results in a history effect and shape memory effect via the ferroelastic phase transition