Lenticular Domains Research Articles

Unusual domain growth during local switching in triglycine sulfate crystals

Formation and growth of isolated lenticular domains created by local switching using a biased tip of the scanning probe microscope in nominally pure triglycine sulfate single crystals have been studied experimentally. The obtained unusual change in the domain shape during growth has been considered in terms of a kinetic approach and attributed to simultaneous stochastic step generation for domain widening and deterministic nucleation (step generation at the domain vertices) for domain elongation. The main parameters of the domain wall motion have been extracted by fitting of the field dependence of the domain length and width. The obtained results provide a useful insight into the features of the domain structure kinetics in the uniaxial ferroelectrics and can be used for development of the domain engineering methods.

In Situ 3D Observation of the Domain Wall Dynamics in a Triglycine Sulfate Single Crystal upon Ferroelectric Phase Transition

We present the first in situ 3D observation of domain wall dynamics close to a ferroelectric–paraelectric phase transition, which we obtain via second‐harmonic generation microscopy (SHGM). Showing a pure second‐order phase transition at its Curie temperature of 49 °C, triglycine sulfate (TGS) is a model ferroelectric material to study such phase transitions. After annealing, in TGS various qualitatively different domain patterns, e.g., stripes or small lenticular domains, have been reported so far. By applying SHGM, we can show that these findings do not necessarily contradict each other. In fact, qualitatively different domain patterns may coexist in the same TGS sample at the same time.

Domain Dynamics of C-Axis Polarization in Bismuth Titanate Crystals

Polarization switching and domain dynamics in unpoled and poled crystals of bismuth titanate by applying electric field along the crystallographic c axis were investigated through polarization measurements and domain observations by optical microscope and piezoelectric force microscope. Poled crystals showed a well-saturated polarization hysteresis with a remanent polarization of 4.4 μC/cm2 and a coercive field of 4.7 kV/cm. Domain observations reveal that lenticular domain acts as an initial nucleus during polarization switching. The sidewise motion of the lenticular-domain walls and resultant single domain state were easily established for the poled crystals, while the lenticular domains observed in unpoled crystals were clamped even though a high electric field was applied to them.

Domain Pattern of Triglycine Sulfate after Exposure to an Electric Field Perpendicular to the Ferroelectric Axis

The change in the domain pattern was observed when the influence of an electric field perpendicular to the ferroelectric axis in triglycine sulfate crystals was investigated. With the charged carbon decoration method, the domain pattern turned out quite changed from a lenticular domain pattern perpendicular to the c axis into a rigid striped one parallel to the c axis. The direction of the stripe, on which the strongest influence of the perpendicular electric field has been found, seems to have a peculiar nature.

Domain Dynamics in Unpoled and Poled Bismuth Titanate Crystals

Domain switching process of bismuth titanate single crystals was investigated under application of electric field along the crystallographic c axis through polarization measurements and domain observations by optical microscope and piezoelectric force microscope. While unpoled crystals exhibited a poor polarization hysteresis, the crystals which were poled at 150°C showed a well-saturated polarization hysteresis with a remanent polarization of 4.4 micro C/cm2 and a coercive field of 4.7 kV/cm. Domain observations reveal that lenticular domain acts as an initial nucleus both in the poled and unpoled crystals during polarization switching of the c-axis component. The sidewise motion of the lenticular-domain walls and resultant single domain state were easily established for the poled crystals, while the lenticular domains observed in unpoled crystals were clamped even though a high electric field was applied to them.

Growth and characterisation of l-cystine doped TGS crystals

Single crystals of l-cystine doped triglycine sulfate (LCTGS) were grown from aqueous solution by low temperature solution growth technique. Morphological changes were observed on the grown crystals. Crystalline quality and cell parameter values were found using rocking curve and powder X-ray diffraction analysis, respectively. The presence of l-cystine in LCTGS was estimated qualitatively by FTIR analysis. Microhardness studies were carried out using Leitz Weitzler hardness tester at room temperature. The dielectric studies were carried out to identify the phase transition temperature and to find the dielectric constant. P-E hysteresis studies were done to find the values of spontaneous polarisation and coercive field for both pure and doped TGS crystals. Scanning electron microscopic investigations on uncoated b-cut plates were carried out to visualise the lenticular domains. AFM studies on the cleaved b-cut plate were carried out to understand the ferroelectric surface and the domain structure.

Commonalties of the influence of lower valent A-site and B-site modifications on lead zirconate titanate ferroelectrics and antiferroelectrics

Studies of the structure-property relations of lead zirconate titanate (PZT) modified with lower valent substitutions on the A- and B-sites have been performed as a function of substituent concentration. These investigations have yielded common changes induced by these substitutions on ferroelectric phases. The commonalties are the presence of fine domains and polarization pinning effects. Differences in domain morphologies were observed between the rhombohedral and tetragonal ferroelectric phases. Rhombohedral ferroelectrics were found to exhibit “wavy” domain patterns with increasing dopant concentrations, whereas a lenticular domain shape was preserved as the domain size was decreased for tetragonal ferroelectrics. These differences were explained in terms of different pinning mechanisms based on the differences in local elastic strain accommodations. Investigations of high Zr-content PZT have revealed that the ferroelectric rhombohedral phase becomes stabilized over the antiferroelectric orthorhombic with increasing concentrations of lower valent modifications. This change was explained in terms of the enhanced coupling between oxygen octahedra due to the bonding of oxygen-vacancy dipoles.

Computer simulation of ferroelastic phase transition in LaNbO4

A model of lanthanum orthoniobate which possesses a ferroelastic tetragonalmonoclinic phase transition is proposed. It contains only one particle per unit cell, but it is constructed consistently with symmetry changes at the phase transition. The model parameters are chosen to reproduce the bare soft mode, degree of deformation of the tetragonal unit cell to a monoclinic one, and the phase transition temperature. The ferroelastic system with free boundary conditions was simulated by the molecular dynamics technique, and the second order phase transition was reproduced. The studied annealing process shows formation of the stripe lenticular domain pattern, which has been interrupted by the appearance of a temporary band of perpendicularly oriented lenticular domains. The maps contain W′-type domain walls whose orientations are fixed only by interplay of potential parameters and not by symmetry elements. The simulated domain pattern has the same features as those observed by transmission electron microscopy.

Domain Structure Investigations of Triglycine Sulfo-Phosphate Single Crystal: Evidence of Domain Motion with Time at Room Temperature

Ferroelectric domain dynamics of triglycine sulfo-phosphate (TGSP) single crystals have been studied by atomic force microscopy (AFM). Lenticular domains have been observed on a cleaved (010) surface at room temperature. Time evolution of surface topography with domain motion has been studied systematically for the first time. Due to spontaneous movement of the domain boundary, there is a removal of the top most layer SO4-G1. Consequently the second top layer (G2-G3) is exposed. Additionally, continuous variations in the refraction of cleavage layers at the domain boundary are documented.

Shape and size controls of micro-domains in LaNbO 4 crystals

Necessary conditions to introduce shear stresses locally in LaNbO 4 crystals and to form lenticular shaped micro-domains are investigated by a computer simulation for a three dimensional and anisotropically elastic continuum. It is shown in an experiment that a pair of lenticular domains of 0.8 μm wide and 20 μm long are introduced by counter forces (about 40 kg/mm 2 each) from two stings of 10 μm at their tips. The possibility of reducing the size of domains to sub-micron scale is discussed.

AFM Observation of Ferroelectric Domains on TGS Cleavage Surface

Utilizing an atomic force microscope (AFM), we observed the cleavage surface of triglycine sulfate [TGS; (NH 2 CH 2 COOH) 3 H 2 SO 4 ] cleaved near Curie point in the atmosphere. Adopting the constant height mode in the repulsive force region, the contrast of lenticular domain patterns reversed for the opposite direction scans parallel to the cleavage direction. The change in the contrast may result from the difference in the frictional force due to the structure of the ferroelectric domains on the cleavage surface.

The Moniaive Shear Zone: a major zone of sinistral strike-slip deformation in the Southern Uplands of Scotland

Synopsis The Moniaive Shear Zone is a recently delineated major zone of enhanced ductile deformation (up to 5 km wide) within the Southern Uplands of Scotland. The northern margin of the zone coincides with the Orlock Bridge Fault at the boundary between Ordovician and Silurian grey-wackes. Outwith the shear zone, the greywackes are typically weakly deformed, with the regional S1 fabric being developed within mudstone interbeds. Within the shear zone, Silurian Gala Group greywackes are deformed by locally pervasive linear and planar fabrics which yield a consistent sinistral sense of shear. The shear-zone fabric, in general, dips steeply towards the NW with its strike being sub-parallel to that of the regional S1 cleavage. Detailed petrological and micro-structural studies have demonstrated that the Moniaive Shear Zone comprises several zones of high strain enclosing lenticular domains of relatively low strain. The relationship between the Moniaive Shear Zone and the Cairnsmore of Fleet Granite indicates that the main phase of ductile movement on the zone occurred prior to 392 Ma although the exact age of ductile deformation on the shear zone is uncertain.

Microstructure and magnetic domain structure in Fe-Pt and Fe-Pd polytwinned alloys

Lorentz microscopy and conventional transmission electron microscopy have been used to characterize the unique magnetic domain configurations associated with the polytwinned microstructures in Fe-Pt and Fe-Pd alloys. The evolution of the domain structures during the disorder (Al) to order (L1/sub 0/) transformation occurring in these alloys has been followed and correlated with the development of the polytwinned state. A transition from serpentine configuration to bands of lenticular domains within emerging macrotwin plates has been revealed using Lorentz microscopy. Two types of domain walls have been identified, namely, crystallographic frozen and mobile walls within the polytwinned structures. A simple model of the domain configurations and local magnetization appears to describe the salient features of the magnetic structure in the Fe-Pt and Fe-Pd alloys. Lorentz microscopy has been used to measure the thickness of the walls in the fully ordered Fe-Pd alloy, giving an approximate value of delta approximately 50-100 AA.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multiple scattering and displacive modulation in the YBa2Cu3O7-δ system

Using transmission electron microscopy, structure modulation associated with electron multiple scattering and diffuse scattering in oxygen reduced, and Fe and Co doped YBa2Cu3O7_δ has been studied. The modulated structure (tweed) exhibits [110] and roughly-periodic lenticular domain images (see Fig.l) and cross-shaped diffuse intensity in diffraction (see Fig.2). The overall diffraction pattern in the [001] zone has a 4-fold symmetry with diffraction intensity which falls off monotonically from one Brillouin zone to the next. Superimposed over each Bragg spot seem to be two cross-streaks of equal length in the [110] and directions.However, for a diffraction pattern in a high symmetry Laue case, one must consider the possibility of multiple scattering effects, whereby a diffracted electron beam acts as an incident beam. This can complicate diffuse scattering phenomena, even in a thin crystal. Careful inspection of Fig.2 reveals that the shapes of the diffuse scattering are not all identical at all diffraction spots.

“Tweed” structure of Fe-doped YBa 2Cu 3O 7−δ

Fe-doped YBa 2Cu 3O 7−δ single crystals have been prepared by a flux method from an Y-Ba-Cu-O precursor with copper partially substituted by iron. Electron diffraction and microscopy were applied to study the domain structure of the material. Superposed on a broad twin band texture, as also observed in undoped material, all samples reveal a finer “tweed” structure of overlapping lenticular domains oriented along [120] and [1 1 0]. This suggests a two-step formation process of the domain structure. The displacement field, corresponding with the tweed structure, resembles that of microtwinning in undoped, quenched YBa 2Cu7 3O 7−δ samples. The randomly dispersed Fe-ions act as pinning centers or fragment the structure by the induction of twin interfaces. Monte Carlo simulations support this idea.

Crystal growth and domain structure of triglycine sulphate doped with Pt(II)

AbstractThe single crystals of triglycine sulphate doped with bivalent Pt‐ions (TGS‐Pt) were grown in full‐shaped form, i.e. with many growth sectors. The domain structure of individual growth sectors was studied by the liquid crystal method. The growth sectors are mostly in a single domain state but spontaneous polarization is reversed in growth sector boundaries, which coincide with charged domain walls. Only the growth sector 001 reveals a blockshaped domain structure, however it differs from usual lenticular domains of the undoped TGS. The concentration of Pt in various growth sectors is different. The growth sectors with the higher concentration of Pt than 3 × 10−2% exhibit the unipolarity stable against thermal schocks.

Microstructure and cleavage development in selected slates

A detailed microstructural study of three slates by high voltage transmission electron microscopy is reported. The slates are mineralogically similar, come from minor fold cores and exhibit differing degrees of cleavage intensity. All three slates have domains of orientated phyllosilicates (cleavage lamellae) which contain only a low percentage of quartz and carbonate. Between these lamellae are lenticular domains which contain deformed phyllosilicates and which are enriched in secondary minerals. The initiation of cleavage lamellae can be clearly observed in electron micrographs from one of the slates studied. It occurs along zones of intense deformation, viz. along kinks and microfolds, which form from initial crenulations that are difficult to detect in a petrological microscope.

Domain structure investigations in triglycine sulphate single crystals

AbstractThe domain structure of pure and irradiated TGS crystals was investigated by electron microscope decoration technique. Changes in the decoration pictures due to irradiation are shown and the way in which small lenticular domains disappear in the spontaneous ageing process is presented. Moreover, the thickness of the domain wall was assessed to be for good TGS crystals, grown in the paraelectric phase, of about 120 Å.

Ferroelectric Domain Structure of Tri-Glycine Sulfate Observed Using a Scanning Electron Microscope

Domain structures in the (010) plane are investigated in the secondary electron mode of S.E.M. The long axis of typical lenticular domains in crystals as grown is along the direction nearly perpendicular to the crystallographic c-axis. Fine lamellar structures appearing in annealed crystals are also along the same direction. The electron beam scanning causes a polarization reversal, and makes possible the direct observation of the dynamical behavior of the domain. The domain boundary has a fairly strong tendency to be perpendicular to the c-axis. The pointed end of the lenticular domain is the position where the domain boundary is caught.