Tetragonal Crystals Research Articles

Thermal Activation of Getters in Magnetron Production Technology

In order to develop a scientifically grounded technology for production of porous getters, there appears the necessity to apply highly sensitive methods for determining the activation temperature, which are compatible with the standard magnetron pumping technology. In this study, a complex technique for determining the activation temperature for porous getters is proposed using the experimental scheme simulating the conditions of porous getter activation in accordance with the standard exhaust tube pumping technology. Under the conditions of the simulation of physicochemical processes in the volume of the heated magnetron housing under pumping, the model of the formation of a gas load on the interior pumping equipment is considered. It is shown that, according to the theory of composite chemical reactions, thermal desorption flows are generated by either the theory of consecutive reactions or the theory of parallel-consecutive reactions. The sorption capacity of porous getters is determined from a plot as the time–temperature dependence of the mass yield of composite chemical reactions of interaction between the gas load and the surface and bulk of a getter tablet. A getter tablet’s change in mass is recorded using the microbalance of a vacuum thermogravimetric unit uninterruptedly at the frequency of one measurement a second throughout the entire period of measurements. The sensitivity threshold of the microbalance is 10–5 g and the maximum mass is 5 g. Using the theory of parallel-consecutive reactions, for the first time, the minimum temperature of thermal activation of a porous getter of a Ti–V (30 at %) alloy is determined, which is the main technological parameter when interior pumping equipment is employed. For the nonisothermal part of the standard heat treatment plot, at the heating rate of 10°C/min and the specified vacuum conditions, the minimum activation temperature is 393°C. For estimating the changes in the roughness of the free surface of a getter washer subjected to interior saturation in a hydrogen medium, scanning electron microscopy is used. Cracks and microsized tetragonal single crystals are found, which might be titanium hydrides TiН2. It is established that crack formation has a positive effect on the getter’s sorption activity due to the appearance of new atomically clean surfaces. However, cracking can contribute to the crumbling of the getter tablet. Therefore, the hydrogen gas load is the factor that limits the durability of the getter.

Mechanical characteristics, structure, and phase stability of tetragonal crystals of ZrO2–Y2O3 solid solutions doped with cerium and neodymium oxides

The phase composition, structure, and mechanical characteristics of ZrO2-based crystals stabilized with yttrium, cerium, and/or neodymium oxides at a total concentration of 2.8 mol% were studied. The stability of the phase composition and the mechanical characteristics of the crystals after annealing in air are considered. The entry of Nd3+ cations into the transformable (t) and nontransformable (t′) tetragonal phases was studied by optical spectroscopy. It was found that partial replacement of Y2O3 with CeO2 or Nd2O3 in ZrO2-based solid solutions results in crystals with high microhardness (~1200 MPa) and high fracture toughness (~12–15 MPa m1/2). Annealing in air at 1200°С leads to a change in the phase composition and a decrease in the crack resistance in (ZrO2)0.972(Y2O3)0.02(СeO2)0.008 crystals. The co-doping of the crystals with CeO2 and Nd2O3 and the predominant arrangement of Nd3+ ions in the t phase prevent the appearance of a monoclinic phase in the bulk of the material and result in high fracture toughness of (ZrO2)0.972(Y2O3)0.02(CeO2)0.004(Nd2O3)0.004 crystals after annealing.

Early Short-Term Postoperative Mechanical Failures of Current Ceramic-on-Ceramic Bearing Total Hip Arthroplasties.

Although ceramic-on-ceramic (CoC) bearings have been shown to produce the smallest amount of wear volume in vitro as well as in vivo studies when used for total hip arthroplasties (THA), concerns about the failure of these bearing surfaces persist due to early failures observed after short postoperative time. In this study, an exhaustive analysis of the early failure occurred on the new generation of ceramic bearings, consisting of a composite alumina matrix-based material reinforced with yttria-stabilized tetragonal zirconia (Y-TZP) particles, chromium dioxide, and strontium crystals, was performed. For this study, 118 CoC bearings from 117 patients were revised. This article describes a group of mechanical failure CoC-bearing BIOLOX THA hip prosthesis patients without trauma history. The retrieved samples were observed under scanning electron microscopy (SEM), composition was analyzed with energy dispersive X-ray spectroscopy (EDX), and damaged surfaces were analyzed by grazing-incidence X-ray diffraction (GI-XRD) and white light interferometry. In the short term, CoC articulations provided similar mechanical behavior and functional outcome to those in XLPE cases. However, 5% more early mechanical failures cases were observed for the ceramic components. Although the fracture rate of third generation CoC couples is low, the present study shows the need to further improve the third generation of CoC-bearing couples for THA. Despite the improved wear compared to other materials, stress concentrators are sources of initial crack propagation, such as those found in the bore-trunnion areas. Moreover, in view of the evidence observed in this study, the chipping observed was due to the presence of monoclinic phase of the Y-TZP instead of tetragonal, which presents better mechanical properties. The results showed that total safety after receiving a THA is still a goal to be pursued.

PEFC Cathode Catalysts of ZrO2/C Prepared By RF Magnetron Sputtering and Crosslinked Polymer Methods

Fuel cells are expected to be clean power generation devices in the future energy society. Various types of fuel cells, which are different in electrocatalysts, electrolytes, and operating temperatures, are available for practical use in various places depending on their characteristic. Among them polymer electrolyte fuel cells (PEFC) have been applied to fuel cell vehicles (FCV), household cogeneration systems and etc. PEFC uses large amounts of Pt for electrocatalysts, which is one of the serious problems for large scale commercialization. The worldwide production of Pt is about 180 ton/year, and about 60 g of platinum is practically used in one FCV. If all of the world production of Pt is used for FCV, only 3 million of FCV can be manufactured in a year, although the annual production of cars in the world is about 100 million. Therefore, the development of electrocatalysts with non-Pt materials is indispensable for the broad spread of PEFC. The cathode catalysts significantly affect to the cell voltage, current density, and durability, so that the developments of alternative cathode materials to conventional Pt-based catalysts are expected. Compounds of oxides of group 4 and 5 elements transition metals such as Zr, Ta, Nb, and Ti, chalcogenides such as Ru and Mo, and carbon materials with N-containing complexes of Fe and Co, carbon materials doped with B and N are intensively investigated in the past decade. In this study, ZrO2/C catalysts were investigated for oxygen reduction reaction (ORR) activity in acidic media. Two types of preparation methods have been examined; radio-frequency magnetron sputtering and crosslinked polymer methods.In magnetron sputtering method, carbon black (CB) powders were stirred in a rotary drum chamber with milling balls and cubes. A Zr metal target was attached to a sputtering gun placed in the stirring drum. Sputtering was performed in 10 Pa of Ar. In crosslinked polymer method, ammonium zirconium carbonate (AZC) was used as a crosslink reagent for polyvinyl alcohol (PVA). Addition of citric acid (CA) was found to be effective. Mixture of AZC, PVA, and CA were well stirred at 80ºC, and CB was immersed in the mixture. The mixture was dried at 300ºC in air and them heat treated 600~1200ºC in N2 or H2. The catalyst ink was obtained by ultrasonically dispersing 300 µL of isopropanol (IPA), 4 mg of catalyst and 12 µL of 5% Nafion-dispersed solution. The sample electrode was prepared by dropping 150 µL of the catalyst ink on glassy carbon (GC) and drying. ORR activity was measured in 0.1 M H2SO4 with O2 bubbling.ORR activity of ZrO2/C catalysts which were prepared by sputtering method was shown in the attached figure. This figure shows ORR properties of ZrO2/C catalysts prepared at various sputtering times in 0.1 M H2SO4. ZrO2/C was pretreated in H2 flow at 1000˚C for 3 h. ORR current was difference between current in O2 and N2 saturated solutions. ORR Current appeared around 0.8 VR HE for the catalysts deposited longer than 40 min. This result indicate ZrO2/C have obvious ORR activity. X ray diffraction (XRD) of ZrO2/C showed the formation of both monoclinic and tetragonal ZrO2 crystals. ZrO2 particles with diameter in several nm scale were observed by transmission electron microscopic (TEM) images, and formation of these particles were concluded to contribute the obvious ORR activity. On the other hand, ZrO2/C catalysts which were prepared by crosslinked polymer methods also showed similar ORR activity to those by sputtering method. The details were discussed in the presentation.This work was supported by ESICB, Kyoto University and New Energy and Industrial Technology Development Organization (NEDO) of Japan. Figure 1

Wave propagation in micromorphic anisotropic continua with an application to tetragonal crystals

We study the coupled macroscopic and lattice wave propagation in anisotropic crystals seen as continua with affine microstructure (or micromorphic). In the general case, we obtain qualitative information on the frequencies and the dispersion relations. These results are then specialized to crystals of the tetragonal point group for various propagation directions: exact representation for the acoustic and optic frequencies and for the coupled vibrations modes are obtained for propagation directions along the tetragonal c-axis.

The coupled AgI/BiOI catalyst: Synthesis, brief characterization, and study of the kinetic of the EBT photodegradation

The relatively novel AgI/BiOI coupled system (CS) was prepared in-situ by mechanical mixing of the as-synthesized AgI and BiOI nanoparticles (NPs) and characterized by various characterization techniques such as XRD, SEM-EDX, and UV–Vis DRS. XRD results showed the hexagonal crystals of AgI and the tetragonal crystals of BiOI in the CS. The grain sizes of 34.1 and 25.6 nm were estimated for the CS by the Scherrer and Williamson-Hall equations, respectively. The bandgap values of 2.7, 1.75, and 1.83 were estimated based on absorption edge wavelengths for AgI, BiOI, and CS samples, respectively. The CS showed a boosted photocatalytic activity towards Eriochrome Black T (EBT). This boosted activity depends on the amounts of the CS-ingredients and the CS with an AgI:BiOI mole ratio of 1:2 showed the highest activity. The photodegradation rate constant of 0.0167 min−1 with a t1/2 value of 41.5 min was obtained from the Hinshelwood plot. Further, the mineralization rate constant of 0.0137 min−1 with a t1/2 value of 50.6 min was obtained by applying the COD results in the Hinshelwood model.

Degeneracy Lifting of Néel, Bloch, and Anti-Skyrmion Crystals in Centrosymmetric Tetragonal Systems

A skyrmion crystal has internal degrees of freedom in terms of vorticity and helicity, which gives rise to fascinating types of skyrmion phases (N\'eel, Bloch, and anti-skyrmion). We show how the degeneracy lifting in tetragonal skyrmion crystals occurs in centrosymmetric itinerant magnets by focusing on microscopic interactions through the Fermi surface instability. We demonstrate that four types of skyrmion crystals can be realized according to the signs of the anisotropic Ruderman-Kittel-Kasuya-Yosida interaction, which are sensitive to band structures, electron fillings, atomic orbitals, and sublattice positions. Our findings might provide a possibility of controlling the types of the skyrmion crystals by electron doping and external pressure rather than relying on the noncentrosymmetric lattice structures.

Elastic properties and electronic structure of tetragonal KDP crystal under polishing pressures from first principles

The elastic properties and electronic structure of tetragonal Potassium dihydrogen phosphate (KDP) under polishing pressures were investigated using the plane-wave pseudopotential method based on density functional theory. The results show that the calculated lattice constant, elastic constants and bandgap agreed well with the results of the experiments and the other calculations at ambient pressure. The elastic constants and the elastic moduli of KDP increase with increasing pressure, but Vickers hardness of KDP decreases. KDP crystal changes from brittleness to ductility beyond the pressure of 3 GPa. The anisotropy of KDP increases and the ratio of [Formula: see text]/[Formula: see text] increases with the increase of pressure. When the pressure reaches 4.5 GPa, the tetragonal KDP will undergo structural phase transition. As pressure increases, the bandgap between and O-2[Formula: see text] and P-3[Formula: see text] states increases. The interatomic distances were shortened under external pressure, and the interaction between K[Formula: see text] and the neighboring H2PO[Formula: see text] was enhanced, which leads to the increase of elastic mechanical properties.

Synthesis, Characterization and Pressure Effect on Structural and Mechanical Properties of MgBi2O6: Solid-State Route and DFT Study

Here we have prepared good quality crystalline sample MgBi2O6 employing the solid-state reaction technique. The synthesized material was characterized by XRD and SEM (scanning electron microscopy). The structural study confirmed that MgBi2O6 possesses a tetragonal crystal configuration (JCPDS PDF#, No. 86-2492) with outstanding crystallinity and a grain size between 200 to 350 nm. The temperature dependence electrical resistivity and conductivity were measured by two probe methods and ensured the semiconducting nature of this material. Using the impedance analyzer and UV-visible spectrophotometer we studied the experimental electronic and optical properties of this material. To explore the hypothetical features of MgBi2O6 we have used first-principles methods that depend on CASTEP code. The band structure analysis also ensured the semiconducting nature of MgBi2O6 with a small band gap of 0.12 eV. The semiconducting behavior of MgBi2O6 with a band gap of 0.12 eV was also observed by the band structure analysis. The Born’s stability criteria were fulfilled by the investigated elastic constants and ensured the stable nature of MgBi2O6. The response of structural and mechanical properties with the pressure of MgBi2O6 was discussed in detail. We have also studied the hypothetical optical properties of MgBi2O6 by CASTEP code.

Higher-Order Weyl Semimetals.

Higher-order topology yields intriguing multidimensional topological phenomena, while Weyl semimetals have unconventional properties such as chiral anomaly. However, so far, Weyl physics remain disconnected with higher-order topology. Here, we report the theoretical discovery of higher-order Weyl semimetals and thereby the establishment of such an important connection. We demonstrate that higher-order Weyl semimetals can emerge in chiral materials such as chiral tetragonal crystals as the intermediate phase between the conventional Weyl semimetal and 3D higher-order topological phases. Higher-order Weyl semimetals manifest themselves uniquely by exhibiting concurrent chiral Fermi-arc surface states, topological hinge states, and the momentum-dependent fractional hinge charge, revealing a novel class of higher-order topological phases.

Synthesis and Photoluminescence Properties of Deep-Red-Emitting CaYAlO4:Cr3+ Phosphors

Deep-red-emitting CaYAlO4:Cr3+ phosphors were synthesized by the sol–gel method followed by heat treatment. The effects of sintering temperature on the phase structure, morphology, and luminescence properties of the phosphors were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy, Raman scattering spectroscopy, energy-dispersive X-ray spectroscopy, steady-state photoluminescence (PL), and time-resolved luminescence spectroscopy. The XRD patterns showed that tetragonal CaYAlO4 crystals with space group I4/mmm were obtained after sintering at > 900°C. These experimental data were consistent with Raman spectra and FESEM images. A deep-red emission band at approximately 742 nm from CaYAlO4:Cr3+ phosphors was observed. This band was attributed to the transitions between the 2Eg and 4A2g energy levels of Cr3+ ions located at the CaYAlO4 host's lattice sites with D3d symmetry. Two absorption bands were recorded at near-ultraviolet and yellow regions. The highest PL intensity was obtained for phosphors with a Cr3+ doping concentration of about 0.7 mol.%. The PL decay dynamics of the materials with different doping Cr3+ concentrations were further investigated. All decay dynamics were featured with multiple decay components. The longest decay component with a lifetime of about 5.5 ms was obtained for the sample with the highest PL intensity. These optical behaviors were correlated with the critical distances of Cr3+ ions for energy transfers. Finally, the temperature dependence of deep-red PL emission was also investigated and discussed.

Lysozyme crystals dyed with bromophenol blue: where has the dye gone?

Protein crystals can easily be coloured by adding dyes to their mother liquor, but most structures of these protein-dye complexes remain unsolved. Here, structures of lysozyme in complex with bromophenol blue obtained by soaking orthorhombic and tetragonal crystals in a saturated solution of the dye at different pH values from 5.0 to 7.5 are reported. Two different binding sites can be found in the lysozyme-bromophenol blue crystals: binding site I is located near the amino- and carboxyl-termini, while binding site II is located adjacent to helices α1 (residues 4-15) and α3 (residues 88-100). In the orthorhombic crystals soaked at pH 7.0, binding of the dye takes place in both sites without significant changes in the unit cell. However, soaking tetragonal crystals with bromophenol blue results in two different complexes. Crystals soaked at pH 5.5 (HEWL-T1) show a single dye molecule bound to site II, and the crystals belong to space group P43212 without significant changes in the unit cell (a = b = 78.50, c= 37.34 Å). On the other hand, crystals soaked at pH 6.5 in the presence of imidazole (HEWL-T2) show up to eight molecules of the dye bound to site II, and display changes in space group (P212121) and unit cell (a = 38.00, b = 76.65, c= 84.86 Å). In all of the structures, the dye molecules are placed at the surface of the protein near to positively charged residues accessible through the main solvent channels of the crystal. Differences in the arrangement of the dye molecules at the surface of the protein suggest that the binding is not specific and is mainly driven by electrostatic interactions.

Raman and infrared phonons in tetragonal ZnP2 and CdP2 crystals: a density functional study

Lattice dynamic properties of the tetragonal modification of ZnP2 and CdP2 crystals (space group P41212, no 92) are calculated within the density functional theory. Theoretical results are shown to compare favorably with available Raman scattering and infrared reflection/transmission experimental data, which allows assignment of Raman-and infrared-active modes to the specific lattice eigenmodes. It is confirmed that several distinct features of vibrational spectra of these compounds steam from the presence of four phosphorous spiraling chains within crystallographic unit cell.

Effect of Substrate and Annealing Ambient on the Conductivity of Sputtered MoSi2 Ceramic Thin Film

In this work, molybdenum disilicide (MoSi2) ceramic thin films were deposited by DC magnetron sputtering on different types of substrates (quartz, glass, p-type silicon, n-type silicon, and barium strontium titanate (BST) buffer layer deposited on silicon). The films were annealed under various ambient conditions (air, N2/99.999%, N2-H2/95–5%) at various annealing times (10–90 min) and temperatures (400–1100°C) to enhance their crystallinity and improve their conductivity. The tetragonal crystal phase, which is the most conductive and stable phase of MoSi2 thin films, was obtained on an n-type silicon substrate that was annealed at 1100°C for 90 min in an atmosphere with pure nitrogen gas flux of 200 L/h. The sheet resistance of the MoSi2 thin films was 0.876 Ω cm−2. The films exhibited a homogeneous glossy metallic surface with surface roughness of 0.35 nm and 3.81 nm for amorphous and annealed thin films, respectively. The high conductivity obtained in this work, in addition to the extraordinary material properties of the MoSi2 ceramic thin film, makes it an attractive candidate for remarkable device applications because of the thermal stability of film conductivity.

On the theoretical and phase field modeling of the stress state associated with ferroelastic twin nucleation and propagation near crack tip

Ferroelastic domain switching is considered as that a twin undergoes a lattice orientation described by a deviatoric eigenstrain in this work. A continuum analysis, based on Eshelby equivalent inclusion theory, is derived to study the nucleation and evolution of twin near a pre-existing crack tip (Mode-I) in a mono-phase tetragonal crystal, in an attempt to achieve a better understanding of the contribution that twinning makes to the toughening effect. The analysis develops progressively from the homogenous isotropic, inhomogeneous isotropic to the general anisotropic conditions; and several analytical solutions are evidenced through phase field simulations. Two important critical stresses, defined as the nucleation stress and the fracture-induced twinning (FIT) stress, are found to determine the twin evolution; specifically, the nucleation stress is related to the twinning in a defect-free solid, and the FIT stress is related to the twinning in the vicinity of crack tip. Moreover, considering the inhomogeneity effect, the change of the stress intensity factor (SIF) due to a ferroelastic twin is derived, which provides evidence that the modulus toughening effect originating from the elastic misfit between the parent and twin can be ignored at a relative low applied SIF. Theoretical analysis and phase field simulations both clarify that the shielding/anti-shielding effect to the crack tip is dependent on the nucleation location and the twin size during evolution. The best toughening formula of a ferroelastic ceramic can be obtained by decreasing the FIT stress and increasing the change of SIF simultaneously through adjusting certain material parameters.

Photocatalytic degradation of methyl orange by Bi 20 TiO 32 –montmorillonite composite

To solve the problem of methyl orange (MO) dye wastewater pollution, TiO2–montmorillonite composite (TiO2–MMT) and Bi20TiO32–montmorillonite composite (Bi20TiO32–MMT) were synthesised by the sol–gel method, and they were used for photocatalytic degradation of MO solution. The results showed that TiO2 in TiO2–MMT existed as the anatase type, and Bi20TiO32 in Bi20TiO32–MMT existed as the tetragonal crystal type. When the dosage of the composite was 0.50 g/l, the initial concentration of the MO solution was 20 mg/l, and the pH was 3, the decolourisation rate of MO solution using TiO2–MMT treating was 87.11%, and it reached 98.50% after Bi20TiO32–MMT treating. When Bi20TiO32–MMT was reused four times, the decolourisation rate of the MO solution was only reduced by 3.5%. The photocatalytic degradation between MO solution and Bi20TiO32–MMT complied with the pseudo-first-order kinetic equation. Holes and superoxide radicals interacted directly with MO during photocatalytic degradation, which reduced the probability of hole–electron recombination, and improved the photocatalytic degradation property of Bi20TiO32–MMT. Bi20TiO32–MMT has excellent stability property, which makes it a good composite in the treatment of dye wastewater.

Structure and phase transformations in scandia, yttria, ytterbia and ceria-doped zirconia-based solid solutions during directional melt crystallization

(ZrO2)0.999-x(Sc2O3)х(Eu2O3)0.001 (х = 0.08–0.11) and (ZrO2)0.889(Sc2O3)0.1(R2O3)0.01 (Eu2O3)0.001 (R = Y, Yb, or Ce) crystals were grown by directional melt crystallization with direct high-frequency heating. The microstructure, phase composition and local structure of the crystals were studied using optical microscopy, X-ray diffraction, Raman scattering and optical spectroscopy. Scandia, yttria and ytterbia were shown to be distributed quite homogeneously in the crystals, and their concentrations corresponded to their contents in the charge. Ceria co-doped crystals exhibited ceria displacement in the longitudinal direction, leading to a decrease in the scandia concentration. We analysed the effect of the crystallization conditions on the formation of microstructure, crystallographic phases and local crystalline structure as a function of crystal length.Two-phase (ZrO2)0.999-x(Sc2O3)х(Eu2O3)0.001 (х = 0.08–0.11) crystals were synthesized using this method. At a Sc2O3 concentration of ≤9 mol.%, tetragonal crystals containing small local regions with cubic structures were obtained. At concentrations above Sc2O3 ≥ 10 mol.%, the crystals contained the pseudocubic (t’’ phase) and rhombohedral zirconia modifications and had an inhomogeneous phase distribution in the longitudinal direction.A study of the (ZrO2)0.889(Sc2O3)0.1(R2O3)0.01(Eu2O3)0.001 (R = Y, Yb, or Ce) crystals showed that only the yttria-doped crystals were homogeneous and had a single-phase composition that comprised only the t” phase. The microstructure of the ytterbia- and ceria-doped crystals varied in the longitudinal direction. These crystals were mixtures of rhombohedral and pseudocubic phases (t’’ phase), and the rhombohedral phase was predominant in the top and bottom portions of the crystals.We show that the experimentally observed variations in the microstructure, local structure and phase composition of the crystals were largely determined by the difference in the thermal pretreatment history of different crystal regions, which is typical of this growth method.

Single-Crystalline Fibers of Deuterated Potassium Dihydrogen Phosphate

Single-crystalline fibers have distinct structures and optical properties comparing with the bulk crystals. In this article, two types of single-crystalline fibers of deuterated potassium dihydrogen phosphate (K(H1−xDx)2PO4, DKDP) are obtained by rapid growth in room-temperature supersaturated solution. X-ray diffraction analysis reveals that these DKDP single-crystalline fibers belong to tetragonal (I-42d) and monoclinic (P21/c) phases, respectively. The crystal structure of the tetragonal DKDP single-crystalline fiber is identical to that of the bulk DKDP tetragonal crystal reported. The lattice parameters of the monoclinic DKDP fiber (with the deuterium content of 55%) are a = 14.6571 Å, b = 4.5187 Å, c = 18.6962 Å, and β = 108.030°, which is a new crystal phase of DKDP. The monoclinic DKDP single-crystalline fiber is metastable at the present experimental condition and readily transit to the corresponding DKDP tetragonal phase in solution and in solid by grinding. The optical experiment shows that the highly deuterated tetragonal DKDP single-crystalline fiber possesses excellent optical guided-wave and effective second-harmonic generation properties. DKDP single-crystalline fibers are expected to be the suitable candidates for fabrication of the miniaturized nonlinear optical devices.

Hydrogen/deuterium exchange behavior in tetragonal hen egg-white lysozyme crystals affected by solution state.

Neutron diffraction studies of hydrogen/deuterium-exchanged hen egg-white lysozyme were performed by a joint X-ray and neutron refinement to elucidate the hydrogen/deuterium exchange behavior. Large crystals for neutron work, consisting of molecules that were exchanged before crystallization, were obtained by repeatedly adding protein solution to the crystal batch using deuterated precipitant reagent. There are differences in hydrogen/deuterium exchange behavior compared with previous crystallographic or NMR studies, which could be due to intermolecular interactions in the crystal or to different lengths of exchange period.

Orientation dependence of dielectric and piezoelectric properties of tetragonal relaxor ferroelectric single crystals by alternate current poling

Piezoelectric and dielectric properties of [001] and [110]-oriented tetragonal Pb(In1/2Nb1/2)-Pb(Mg1/3Nb2/3)-PbTiO3 (PIN-PMN-PT) single crystals (SCs) after alternate current poling (ACP) were investigated. Compared with direct current poling (DCP), the piezoelectric and dielectric properties of [001]-oriented samples have no improvement, while the piezoelectric coefficient d33 and free dielectric constant ε33T/ε0 of [110]-oriented samples increase by 32% and 26%, respectively. The domain was observed on (001) and (11¯0) faces of [110]-oriented samples. The enhancement of the piezoelectric performance is attributed to the high density of domain wall, increase of distorted regions between 90° domains, and monoclinic phase. Compared with DCP, both intrinsic and extrinsic contributions enhance after ACP though the Rayleigh analysis. This work indicates that ACP is an effective way to enhance piezoelectric properties of non-polar axis oriented relaxor-PT ferroelectric SCs.