Interaxial Angles Research Articles

The Effect of Strain on the Optical Properties of Quartz: Point-Dipole Calculations

Abstract Strained quartz commonly shows biaxial optical properties with 2Vγ up to ∼22°. This research uses point-dipole theory to calculate the optical properties of α-quartz strained in various ways. Strain was modeled by distorting the lattice. Calculations that relate to simple a-axis compression involve decreasing the a-axis in small increments. Shear strain is modeled by altering the interaxial angles in small increments. The calculations agree with published experiments and observations on natural quartz tectonites. The methodology is transferable to other minerals. Point-dipole theory, as applied in this study, has the potential for quantifying the stress responsible for optical manifestations of strain in minerals. The strategy may be useful for designing laboratory experiments, understanding experimental results, and interpreting petrographic observations.

Nasal Measurements in Indian Population of North-East Region: Angular Parameters with Literature Review.

Just like linear nasal parameters, angular nasal parameters form the basis of any rhinoplasty, especially in various ethnic groups to maintain the specific racial characteristics while creating an aesthetic nose. The objective of this study was to measure and study the outcomes of angular nasal parameters in north-east Indians and to contrast them with available literature on Oriental, Caucasian and Indian population in general. This cross-sectional study was carried out in 150 young adults from north-east region of India. Surface landmarks were marked, and standard photographs were taken. Nine angular parameters were measured from the left lateral and basal view photographs of the face using computer software. Data were analysed by Student's 't'-test for parametric data and Mann-Whitney U-test for non-parametric data using SPSS v.25. All the angular measurements were found to be greater in females except nasofacial angle, columella tip angle and interaxial angle. Differences in nasofrontal angle, columella labial angle, nasofacial angle and columella tip angle between males and females were statistically significant. Nasofrontal and columella labial angles were more acute in the study population compared to Caucasians, Orientals and other Indians while nasofacial, interaxial and interalar angles were larger. The north-east Indian nose is dissimilar to that of rest of the country as well as that of Caucasians and Orientals with respect to angular parameters.

Enhanced Ferroelectric Polarization in Epitaxial BiFeO3−BiMg2/3Nb1/3O3 Films

Remanent polarization is a key parameter of a ferroelectric material. A large remanent polarization is favorable for various ferroelectric applications. Here, we report a large remanent polarization of 116.8 \ensuremath{\mu}C ${\mathrm{cm}}^{\ensuremath{-}2}$ observed in ${\mathrm{Bi}\mathrm{Mg}}_{2/3}{\mathrm{Nb}}_{1/3}{\mathrm{O}}_{3}$ (BMN)-modified ${\mathrm{Bi}\mathrm{Fe}\mathrm{O}}_{3}$ (BFO) thin films, epitaxially deposited on (001)-oriented ${\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_{3}$ substrates buffered with ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{Mn}\mathrm{O}}_{3}$ electrodes. Combined experimental analyses and first-principles calculations reveal that the incorporation of 10 mol % BMN into BFO increases both the intrinsic and extrinsic contributions, resulting in doubled polarization. The intrinsic polarization calculated for BFO-BMN is larger than that of BFO due to enhanced ionic displacements. Compared with epitaxial BFO films in a rhombohedral structure with an interaxial angle of \ensuremath{\alpha} = 89.72\ifmmode^\circ\else\textdegree\fi{} and quasitetragonal c/a = 1.018, the epitaxial BFO-BMN films become more tetragonal-like, with \ensuremath{\alpha} = 89.91\ifmmode^\circ\else\textdegree\fi{} and c/a = 1.037. Moreover, a unique rotated twinning-domain structure is developed in the BFO-BMN thin films, further increasing the out-of-plane polarization by rotating the [111] direction toward the film's normal. These results provide additional opportunities to increase ferroelectric polarization through composition engineering.

AXOIDS OF HOOKE’S JOINT

The analysis of literary sources devoted to the research and construction of cardan transmissions using the Hooke's joint showed that the peculiarities of the spherical movement of the cardan joint crosspiece are insufficiently covered. This is explained by the relatively small weight of the crosspiece, due to which it almost does not affect the dynamics of the cardan transmission. The need to take into account the mass-geometric parameters of the crosspiece and to analyze comprehensively its movement may arise during accurate calculations of high-speed cardan transmissions. In this case, it is convenient to consider the movement of the crosspiece as rolling without sliding of the moving axoid on the stationary axoid. This approach makes it possible to more fully investigate the peculiarities of the spherical movement of the crosspiece and gives a visual representation of the orientation of its instantaneous axis of rotation in fixed and moving coordinate systems. Based on this, this work is devoted to the construction of a kinematic model of the Hooke's joint crosspiece, the movement of which is considered as rolling without sliding of a moving axoid on a stationary one.
 As a result of the kinematic analysis of the Hooke's joint, the equations of the hodographs of the vector of the absolute angular velocity of the crosspiece in the fixed and moving coordinate systems were obtained, and the parameters of the fixed and moving axoids of the crosspiece of the cardan joint were determined. It is proved that the stationary axoid of the crosspiece of the Hooke's joint is an oblique elliptic cone with the apex in the center of the crosspiece, and its opposite generatrices, crossing the major axis of the guide ellipse, coincide with the axes of the drive and driven shafts of the joint. The moving axoid of the crosspiece is a closed conical surface with a variable opening angle, the maximum value of which is equal to twice the value of the interaxial transmission angle. With small values of the interaxial angle, which occur in the practice of using a single Hooke’s joint, a moving axoid can be approximately considered as a straight circular cone with a vertex in the center of the crosspiece and an opening angle equal to twice the value of the interaxial transmission angle. The error of this assumption increases rapidly with the increase of the interaxial transmission angle. The correctness of the obtained mathematical model was confirmed by computer modeling in the Autodesk Inventor environment.
 The obtained results can be used in the study of dynamic processes that occur in cardan transmissions using Hooke's joint.

High-Power Factor Enabled by Efficient Manipulation Interaxial Angle for Enhancing Thermoelectrics of GeTe-Cu2Te Alloys.

The emerged strategy of manipulating the rhombohedral crystal structure provides another new degree of freedom for optimizing the thermoelectric properties of GeTe-based compounds. However, the concept is difficult to be effectively measured and often depends on heavy doping that scatters carriers severely. Herein, we synergistically manipulate lattice distortion and vacancy concentration to promote the excellent electrical transport of GeTe-Cu2Te alloys and quantify the interaxial angle-dependent density of state effective mass. Distinct from the conventional electronic coupling effect, about 2% substitution of Zr4+ significantly increases the interaxial angle, thereby enhancing the band convergence effect and improving the Seebeck coefficient. In addition, Ge-compensation attenuates the mobility deterioration, leading to improved power factor over the whole temperature range, especially exceeding ∼22 μW cm-1 K-2 at 300 K. Furthermore, the Debye-Callaway model elucidates low lattice thermal conductivity due to strong phonon scattering from Zr/Ge substitutional defects. As a result, the highest figure of merit zT of ∼1.6 (at 650 K) and average zTave of ∼0.9 (300-750 K) are obtained in (Ge1.01Zr0.02Te)0.985(Cu2Te)0.015. This work demonstrates the effective band modulation of Zr on GeTe-based materials, indicating that the modification of the interaxial angle is a deep pathway to improve thermoelectrics.

Anomalous enhancement of thermoelectric performance in GeTe with specific interaxial angle and atomic displacement synergy

Discovery and engineering of novel phase structures pave new avenues in the study of phonon-electron decoupling in thermoelectric materials, with the final aim of enhancing their figure of merit ZT . Here, we report a metastable GeTe phase that shows coexisting cubic and rhombohedral phases and enhances the ZT of GeTe-based alloys to ∼0.8 at 300 K and ∼1.3 at 373 K. This is comparable with the state-of-the-art Bi 2 Te 3 -based alloys in the low-temperature range. The ZT enhancement shows a positive correlation with an increased contribution of a special rhombohedral GeTe phase with synergetic specific interaxial angle and atomic displacement, which triggers a multiple-band convergence for enhancing carrier mobility. Moreover, quenching-induced extra phase boundaries and enhanced anharmonicity may cause extra phonon scattering that reduces the lattice thermal conductivity. This work highlights the importance of precision designing phase structures for solving the phonon-electron coupling problem in thermoelectric materials. • A metastable GeTe with coexisting cubic and rhombohedral phases is revealed • An r-GeTe with a specific interaxial angle and atomic displacement is extracted • Weight carrier mobility can be dramatically increased by engineering this phase • The obtained thermoelectric performance is comparable with Bi 2 Te 3 Phase engineering provides an avenue to realize phonon-electron decoupling in thermoelectric materials. Wang et al. reveal a metastable GeTe with coexisting cubic and rhombohedral phases where the rhombohedral GeTe with synergetic specific interaxial angle and atomic displacement triggers multiple-band convergence for sharply increasing the carrier mobility.

Synergistically Optimized Thermal Conductivity and Carrier Concentration in GeTe by Bi-Se Codoping.

The GeTe compound has been revealed to be an outstanding thermoelectric compound, while its inherent high thermal conductivity restricts further improvement in its performance. Herein, we report a study on the synergistic optimization of the thermoelectric performance of GeTe by Bi-Se codoping. It is shown that the introduction of Bi decreases the carrier concentration and increases the structural parameter of the interaxial angle. With Se doping in the Te site, the lattice thermal conductivity is markedly reduced, while the carrier mobility is slightly influenced. Compared with the singly Se-doped GeTe, the Ge1-xBixTe1-ySey samples are more closed to a cubic phase, as indicated by the larger interaxial angle. On account of the reduction of carrier concentration and thermal conductivity, a ZTmax of 1.80 at 665 K and a high ZTave of 1.39 (400-800 K) are obtained in Ge0.94Bi0.06Te0.85Se0.15. This work reveals that the interaxial angle is vital to the performance optimization of rhombohedral GeTe.

Enhanced stability and rate performance of zinc-doped cobalt hexacyanoferrate (CoZnHCF) by the limited crystal growth and reduced distortion

Cobalt hexacyanoferrate (CoHCF) is a potential cathode for aqueous Na-ion batteries due to its high theoretical specific capacity (170 mAh g−1); however, its lower rate capability and cyclability limit its applications. Structural distortion at a weak N-coordinated crystal field during cycling disintegrates Co, yielding an irreversible reaction. Different Zn amounts ranging 0–1 were added to the Co site to suppress the structural irreversibility of CoHCF, yielding Co1-xZnxHCF powder; this Zn (x ≤ 0.09) addition reduced the powder’s dimension because the lower four coordination of Zn–N, not the six coordination of Co–N, limits the powder growth. Simultaneously, a small lattice parameter and interaxial angle (∼90°) are obtained, implying that a narrower Co1−xZnxHCF inner structure is formed to accommodate Na ions. Moreover, the electronic conductivity of Co1−xZnxHCF gradually increased within 0–0.09 range. A smaller particle size with a high surface area leads to a near-surface-limited redox process, similar to a capacitive reaction. Both the surface-limited reaction and electronic conductivity enhances the reversibility due to the smaller charge transfer resistance at the electrode/electrolyte interface caused by Zn addition. Replacing redox-active Co with non-active Zn amount of 0.07 (Co0.93Zn0.07HCF) slightly reduces the specific capacity from 127 to 119 mAh g−1 at 0.1 A g−1 due to the shrunken Co charging sites. Rate performance is enhanced by compromising the capacity and reduced distortion, resulting in 81% retention at a 20-times-faster charging rate. Notably, the Co0.93Zn0.07HCF sample exhibited the good stability while preserving 74% of the initial capacity at 0.5 A g−1 after 200 cycles.

Modulating the chiral nanoarchitecture of cellulose nanocrystals through interaction with salts and polymer

HypothesisThe conditions to allow self-assembly of cellulose nanocrystal (CNC) suspensions into chiral nematic structures are based on aspect ratio, surface charge density and a balance between repulsive and attractive forces between CNC particles. ExperimentsThree types of systems were characterized in suspensions and subsequently in their solid dried films: 1) neat water dialyzed CNC, 2) CNC combined with polyethylene glycol(PEG) (CNC/PEG), and 3) CNC with added salt (CNC/Salt). All suspensions were characterized by polarized optical microscope (POM) and small angle X-ray scattering (SAXS), while the resultant dried films were analyzed by reflectance spectrometer, scanning electron microscope (SEM) and SAXS. FindingsThe presence of chiral nematic (CN*) structures was not observed in dialyzed aqueous suspensions of CNC during water evaporation. By introducing salts or a non-adsorbing polymer, chirality was apparent in both suspensions and films. The interaxial angle between CNC rods increased when the suspensions of CNC/PEG and CNC/salt were dried to solid films. The angle was found to be dependent on both species of ions and ionic strength, while the inter-particle distance was only related to the salt concentration, as explained in terms of interaction energies. The CNC suspensions/film chirality can be modulated by controlling the colloidal forces.

Improved thermoelectric performance of GeTe via efficient yttrium doping

Optimization of the carrier concentration by doping/alloying is a key prerequisite for improving thermoelectric performance. In reality, it is, however, challenging to identify effective dopants in some specific systems. Herein, we discovered that Y doping significantly reduced the carrier concentration, enhanced the power factor, and, therefore, boosted thermoelectric performance. The high Y-doping efficiency had origin in the fact that the compensating effect due to Ge vacancies was weaker in comparison to other dopants in GeTe because the slightly increased rhombohedral interaxial angle suggested that the Ge-vacancy concentration would not be altered dramatically. In addition, first-principles calculations revealed that Y doping did not induce significant modifications on the band structure, consistent with electrical transport measurement results. Moreover, Bi doping was found to be more powerful than Sb doping to further increase electrical resistivity and to enhance performance in which the highest peak ZT ∼ 1.8 together with a high average ZT ∼ 1.1 from 300 K to 723 K was achieved. Our work not only highlighted the efficacy of Y doping in enhancing the thermoelectric performance of the GeTe system but also developed advanced GeTe-based materials for power generation applications.

Reconstruction of Alar Lining and Nostril Base by Oral Mucosal Flap on Muscular Pedicle

Background: Nostril base and Alar wings are forming the major part of the nasal vestibule. This study proposes an innovative technique for functional restoration of alar lining and nostril base by myomucosal oral flap. It also evaluates the functional and aesthetic results of this technique after reconstruction of the nostril and alar subunits. Patients and Methods: Case series study for the proposed technique. Study duration is one year, from start of 2018 till start of 2019. Each patient followed for 6 months. Study setting is a university-based plastic surgery practice. 12 Patients were complaining of unilateral nasal opening distortion due to scars. They included in consecutive sample. Proposed technique was operated on patients who underwent nostril base and Alar lining reconstruction. Objective morphological analysis is done for; the nasal width, mid-columella alar curvature distance, inter-axial angle and two nostril axis angles as well as the comparison of nasal pattern. Subjective analysis of patient's rating for breathing and aesthetic satisfaction level was reported. Results: Functional and aesthetic outcomes were achieved from excellent to good. Breathing from the reconstructed nasal opening returned to the normal pre-scaring status in all cases. Conclusion: To our knowledge, this article proposes a new innovative technique for functional reconstruction of Alar lining and nostril base by oral mucosal flap based on muscular pedicle. It could be a reliable, simple and straight forward technique.

ФОРМИРОВАНИЕ ЗУБЧАТЫХ ПЕРЕДАЧ ИЗ ЭВОЛЬВЕНТНО-КОНИЧЕСКИХ КОЛЕС

When designing modern machine drives based on traditional gears, in some cases there are problems associated with the complexity of the rational layout of the drive, and its load capacity. These problems can be solved using gears with involute bevel wheels. The involute bevel gear (IBG) is the most common case of gearwheel with an involute tooth profile. In IBG, when teeth are formed, the tool displacement coefficient varies linearly along the width of the gear rim. The geometry of the IBG and the gears made up of them was developed at the Department of Technical Mechanics, a branch of SUSU in Zlatoust. The article presents the main dependencies necessary for determining the size of the IBG and possible schemes for the formation of gears with the IBG. Gearings on the base can be formed at any position of the axles of the gears in space. This paper presents schemes for the formation of spatial (on intersecting axes), bevel (on intersecting axes), cylindrical (on parallel axes) transmissions with IBG. The advantages of gears with IBG (layout, operational, load) in relation to gears from traditional cylindrical and bevel wheels are shown. Thus, transmissions from the IBG on intersecting axes make it possible to transmit rotation at arbitrarily small distancesbetween the axles of the wheels with the required contact localization, up to obtaining a linearcontact in gearing of the teeth. Bevel gears with IBG are less sensitive to errors and can be formed at small interaxial angles, which is problematic for traditional bevel gears. Cylindrical gears with IBG differ from traditional ones in increased load capacity and smooth operation. In addition, they can be used as backlashless and single-sided gears. Thus, gears with IBG due totheir versatility and advantages over traditional gears can be successfully used in modern drives(aviation, space, automobile, etc.) with any arrangement of gear axles in space.

Thermal expansion of the Al2SiO5 polymorphs, kyanite, andalusite and sillimanite, between 10 and 1573 K determined using time-of-flight neutron powder diffraction

Powder and single-crystal diffraction data measured from the three geologically important Al2SiO5 polymorphs, kyanite, andalusite and sillimanite, over the last six decades have given varying accounts of each polymorph’s thermal expansion, the scatter between and even within experimental datasets often being quite large. Furthermore, there are no lattice parameter determinations below 273 K, where the thermodynamic functions vary substantially, and few measurements above 1200 K. Accurate and precise lattice parameters of natural kyanite, andalusite and sillimanite have therefore been obtained in the range 10–1573 K using the high-resolution powder diffractometer (HRPD) at the ISIS neutron spallation source. Accuracy is ensured by the use of an internal standard (NIST silicon SRM640c) and use of a bulk probe (neutrons) to avoid the specimen-displacement corrections required by typical back-reflection X-ray diffraction methods. Precision is ensured by use of the time-of-flight method on one of the longest primary neutron flightpath instruments in the world. For kyanite, the improved precision reveals the true temperature dependence of the three inter-axial angles for the first time, permitting derivation of accurate thermal expansion tensor coefficients. For both andalusite and sillimanite, the measurements reveal hitherto unknown regions of substantial negative linear expansivity below room temperature, along the c-axis in andalusite and along the a-axis in sillimanite. Above 1200 K, sillimanite exhibits an anomalous increase in thermal expansion that may be due to a change in the Al/Si tetrahedral site ordering.

Three-dimensional printing of a tunable graphene-based elastomer for strain sensors with ultrahigh sensitivity

A graphene-based elastomer for sensors with tunable and high sensitivity was fabricated by using three-dimensional printing, in which a printable ink was developed by homogenizing graphene and polydimethylsiloxane (PDMS). To make the elastomer tunable and highly sensitive, different microstructures of three-dimensional graphene-PDMS (3DGP) can be formed. Attributed to its well-interconnected scaffolds and designed microstructures, 3DGP demonstrates a series of multifunctional properties, such as excellent stability and a large gauge factor (up to 448 at 30% strain). 3DGP has continuously stable piezoresistive behavior, even after 100 compress-release cycles under 10% strain. By considering the essential properties of 3DGP scaffolds, such as filament diameter, interaxial angle and interlayer space, the printed 3DGP structure can be tunable and highly sensitive. The controllable design and scalable fabrication of the 3DGP advanced functional material suggests that tunable strain sensors and wearable devices have great potential for different applications, which is a finding that can be referenced by future studies on 3D graphene-based sensors.

Accurate determination of low-symmetry Bravais unit cells by EBSD

Unit cells lack of symmetry are difficult to determine accurately, compared to high-symmetry unit cells with many constraints. The electron backscatter diffraction (EBSD) technique in scanning electron microscopy (SEM) was considered inadequate for this task because of the highly defective band detections. We develop a new method for the Kikuchi-band detections, which can improve the accuracy of the EBSD technique in determining the lattice constants of totally unknown Bravais unit cells with low symmetry. The results show that, under ideal conditions (i.e., low-noise EBSD patterns and known projection center), the relative error of the unit-cell constants (a, b, c) is less than 0.3%, and that of the axial ratios (a/b, b/c, c/a) is less than 0.5%. The absolute errors of the inter-axial angles (α, β, γ) and crystal orientations are about 0.1°. Our method is perhaps not as accurate as the classical techniques such as X-ray diffraction, but is demonstrated as a practical tool for crystallographic characterization especially on low-fraction phases, and could be easily incorporated into an SEM to make the most of the SEM in the area of microanalysis.

Temperature-induced first-order displacive phase transition of isonicotinamide-4-methoxybenzoic acid co-crystal

Isonicotinamide-4-methoxybenzoic acid co-crystal (1), C6H6N2O·C8H8O3, is formed through slow evaporation from methanol solution and it undergoes a first-order isosymmetry (monoclinic I2/a ↔ monoclinic I2/a) structural phase transition at Tc = 142.5 (5) K, which has been confirmed by an abrupt jump of crystallographic interaxial angle β from variable-temperature single-crystal XRD and small heat hysteresis (6.25 K) in differential scanning calorimetry measurement. The three-dimensional X-ray crystal structures of (1) at the low-temperature phase (LTP) (100, 140 and 142 K) and the high-temperature phase (HTP) (143, 150, 200, 250 and 300 K) were solved and refined as a simple non-disordered model with final R[F2 > 2σ(F2)] ≃ 0.05. The asymmetric unit of (1) consists of crystallographically independent 4-methoxybenzoic acid (A) and isonicotinamide (B) molecules in both enantiotropic phases. Molecule A adopts a `near-hydroxyl' conformation in which the hydroxyl and methoxy groups are positioned on the same side. Both `near-hydroxyl' and `near-carbonyl' molecular conformations possess minimum conformational energies with an energy difference of < 0.15 kJ mol-1 from a potential energy surface scan. In the crystal, molecules are joined into linear ABBA arrays by intermolecular N-H...O and O-H...N hydrogen bonds which were preserved in both phases. However, these ABBA arrays are displaced from planarity upon LTP-to-HTP transition and the changes in inter-array interactions are observed in two-dimensional fingerprint plots of their Hirshfeld surfaces. The PIXEL energies of each molecular pair in both phases were calculated to investigate the difference in intermolecular interaction energies before and after the displacement of ABBA arrays from planarity, which directly leads to the single-crystal-to-single-crystal phase transition of (1).

The tilt-dependent potential of mean force of a pair of DNA oligomers from all-atom molecular dynamics simulations

Electrostatic interactions between DNA molecules have been extensively studied experimentally and theoretically, but several aspects (e.g. its role in determining the pitch of the cholesteric DNA phase) still remain unclear. Here, we performed large-scale all-atom molecular dynamics simulations in explicit water and 150 mM sodium chloride, to reconstruct the potential of mean force (PMF) of two DNA oligomers 24 base pairs long as a function of their interaxial angle and intermolecular distance. We find that the potential of mean force is dominated by total DNA charge, and not by the helical geometry of its charged groups. The theory of homogeneously charged cylinders fits well all our simulation data, and the fit yields the optimal value of the total compensated charge on DNA to ≈65% of its total fixed charge (arising from the phosphorous atoms), close to the value expected from Manning’s theory of ion condensation. The PMF calculated from our simulations does not show a significant dependence on the handedness of the angle between the two DNA molecules, or its size is on the order of . Thermal noise for molecules of the studied length seems to mask the effect of detailed helical charge patterns of DNA. The fact that in monovalent salt the effective interaction between two DNA molecules is independent on the handedness of the tilt may suggest that alternative mechanisms are required to understand the cholesteric phase of DNA.

Anomalous optical variations in the grossular garnet from the Eden Mills, Belvidere Mountain (Vermont, USA)

The optical anomalies, and surface and lamellar textures of a birefringent grossular garnet crystal from the Eden Mills, Belvidere Mountain, Vermont, USA, have been investigated by optical polarizing microscope, electron-probe micro-analyzer, back-scattered electron imaging, infrared spectroscopy, and single-crystal X-ray diffractometer from the standpoint of crystal growth. This grossular shows one-to-one correlation between natural surface features and its internal textures under crossed polarizers. Electron-probe micro-analyzer (EPMA) gave average chemical composition in (110) thin section, of bright lamella {Ca2.97Mn0.06}∑3.03 [Al1.59Fe0.37Ti0.01]∑1.97(Si3.00)∑3.00 (Gros79.5And18.9Sps1.6) and of dark host {Ca2.99Mn 0.06}∑3.05 [Al1.73Fe0.26 Ti0.01]∑2.00(Si2.97OH0.03)∑3.00 (Gros85.4And13Sps1.6). The correspondence of surface features and the internal textures with spiral or pyramidal growth mechanism suggest that the internal textures of the Eden Mills grossular are formed during growth process. The optical vibrational orientations and the growth steps inclination along [001] and \( \left[\overset{-}{1}10\right] \) directions predict monoclinic symmetry. With X-ray diffractometer (XRD) method, pseudocubic parameters are a = 11.839(2) A, b = 11.855(1) A, and c = 11.868(2) A with interaxial angles α = 90.00(1)°, β = 89.99(1)°, and γ = 90.02(2)° that show orthorhombic symmetry of this crystal. Lamellar texture of Al3+-rich host with Fe3+-rich lamella infers cation ordering at octahedral site of the garnet structure. IR data favors the non-cubic orientation of [(OH) 4] at tetrahedral position in this grossular structure.

Structural characterization of the electric field-induced ferroelectric phase in Na0.5Bi0.5TiO3-KNbO3 ceramics

(1−x)Na0.5Bi0.5TiO3-xKNbO3 (NBT-xKN) ceramics, with x in the range 0.01–0.09, were prepared by solid state reaction and conventional sintering. A progressive transformation from a nano-polar to a long-range ordered ferroelectric phase was observed after the application of a cyclic electric field with an amplitude of 5kVmm−1. It is shown by analysis of the crushed ceramic pellets, using high resolution synchrotron x-ray diffraction, that the application the cyclic electric field induced an irreversible transformation from a pseudo-cubic nano-polar phase to a rhombohedral ordered ferroelectric phase having R3c symmetry. Furthermore, a systematic variation, from 89.6° to 90°, was observed in the rhombohedral interaxial angle as the KN content increased from 1 to 9%. By comparing the structural evidence with the ferroelectric polarization-electric field hysteresis loops, it is shown that the electric field-induced transformation is partially reversible for NBT-5KN and completely reversible or nonexistent for NBT-9KN.

Experimental investigation of the structure, magnetic moment and decomposition process on heating in dipotassium tartarte crystals grown in chemical reaction gel method

Single crystals of dipotassium tartrate were grown in gel by chemical reaction method. The various functional groups such as OH stretching, CH stretching, CC modes, carbonyl modes and metal-oxygen stretching have been identified by using FTIR study. From the powder X-ray diffraction (XRD) studies, the unit cell dimensions and inter-axial angles were found to be a=9.8845Å, b=7.4420Å, c=8.8480Å; α=β=90˚, γ≠90°. This reveals the monoclinic nature of the crystal. The magnetic susceptibility and magnetic moment of the grown crystals have been found to be 36.12×10−6emu and 2.94BM, respectively. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) of the sample exhibit the decomposition process and the loss of weight during the process. The endothermic peak at 285.40°C confirms the major stage of decomposition of the sample and there is no water of hydration.