Showing papers on "Orthorhombic crystal system published in 2002"
TL;DR: In this paper, a magnetic-field-induced strain of about 9.5% was observed at ambient temperature in a magnetic field of less than 1 T in NiMnGa orthorhombic seven-layered martensitic phase.
Abstract: Giant magnetic-field-induced strain of about 9.5% was observed at ambient temperature in a magnetic field of less than 1 T in NiMnGa orthorhombic seven-layered martensitic phase. The strain proved to be caused by magnetic-field-controlled twin boundary motion. According to an analysis of x-ray diffraction data, the crystal structure of this phase is nearly orthorhombic, having lattice parameters a=0.619 nm, b=0.580 nm, and c=0.553 nm (in cubic parent phase coordinates) at ambient temperature. Seven-layer shuffling-type modulation along the (110)[110]p system was recorded. The results of mechanical tests and magnetic anisotropy property measurements are also reported.
1,494 citations
TL;DR: In this paper, the orientation relationship between the orthorhombic superlattice and the rutile structured SnO2 was determined to be [001]o || [102]t and (100)o'||'(010)t for the nanowires and sandwiched nanoribbons.
Abstract: Nanowires, sandwiched nanoribbons, and nanotubes of SnO2 are synthesized using elevated temperature synthesis techniques, and their structures are characterized in detail by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition to the normal rutile structured SnO2, it has been possible to form an orthorhombic superlattice-like structure in the present study. The orthorhombic structure can form in a thin nanowire, coexist with the normal rutile structured SnO2 in a sandwiched nanoribbon, or occur in the form of nanotubes. This result is distinct from that for bulk SnO2 where pressures in excess of 150 kbar are required to form the orthorhombic form. The orientation relationship between the orthorhombic SnO2 and the rutile structured SnO2 is determined to be [001]o || [102]t and (100)o || (010)t for the nanowires and sandwiched nanoribbons, and [001]o || [3 ]t and (110)o || (451)t for the nanotubes. Although the growth direction of the rutile structured SnO2 nanowires i...
504 citations
TL;DR: One-dimensional nanostructures of orthorhombic molybdenum trioxide (α-MoO3) have been synthesized in the forms of ribbons or rods via acidification under hydrothermal conditions at 140−200 °C as mentioned in this paper.
Abstract: One-dimensional nanostructures of orthorhombic molybdenum trioxide (α-MoO3) have been synthesized in the forms of ribbons or rods via acidification under hydrothermal conditions at 140−200 °C The reaction path has been revealed with our kinetic investigations, which shows the following sequence: (i) from the starting compound (NH4)6Mo7O24·4H2O to (ii) formation of intermediate compound ((NH4)2O)00866·MoO3·0231H2O, and then to (iii) final α-MoO3 nanoribbons or nanorods in 100% phase purity The optimal growth temperature is in the range of 170−180 °C under the current experimental settings At higher reaction temperatures, this transformation can be accelerated, but with poorer crystal morphological homogeneity It has been found that the dimensions of these rectangular nanorods are about 50 nm in thickness, 150−300 nm (mean value at 200 nm) in width, and a few tens of micrometers in length The crystal morphology can be further altered with inorganic salts such as NaNO3, KNO3, Mg(NO3)2, and Al(NO3)3
344 citations
TL;DR: In this paper, high-resolution neutron powder diffraction and single crystal measurements on the ferromagnetic shape memory compound Ni2MnGa have been carried out, which enabled the sequence of transformations which take place when the unstressed, stoichiometric compound is cooled from 400 to 20 K to be established.
Abstract: High resolution neutron powder diffraction and single crystal measurements on the ferromagnetic shape memory compound Ni2MnGa have been carried out. They enabled the sequence of transformations which take place when the unstressed, stoichiometric compound is cooled from 400 to 20 K to be established. For the first time the crystallographic structure of each of the phases which occur has been determined. At 400 K the compound has the cubic L21 structure, and orders ferromagnetically at TC ≈ 365 K. On cooling below ~ 260 K a super-structure, characterized by tripling of the repeat in one of the 110cubic directions, forms. This phase, known as the pre-martensitic phase, persists down to the structural phase transition at TM ≈ 200 K and can be described by an orthorhombic unit cell with lattice parameters aortho = 1/√2acubic, bortho = 3/√2acubic, cortho = acubic and space group Pnnm. Below TM the compound has a related orthorhombic super-cell with bortho ≈ 7/√2acubic, which can be described within the same space group. The new modulation appears abruptly at TM and remains stable down to at least 20 K.
303 citations
TL;DR: In this paper, the authors used powder neutron diffraction data to study the crystal structures of the four-layer Aurivillius-phase ferroelectrics Bi5Ti3FeO15 (at 251C) and SrBi4Ti4O15(at a series of temperatures up to 8001C).
187 citations
TL;DR: Two new iron(III) phosphates have been synthesized from the dehydration of hydrothermally prepared monoclinic and orthorhombic hydrated phosphates FePO(4), with electrochemical and magnetic data consistent with the structures of these two compounds.
Abstract: Two new iron(III) phosphates, FePO4, have been synthesized from the dehydration of hydrothermally prepared monoclinic and orthorhombic hydrated phosphates FePO4·2H2O. The structures of both hydrates were redetermined from single crystal data. On dehydration, a topotactic reaction takes place with only those bonds associated with the water molecules being broken, so that both FePO4 phases have essentially the same Fe−P backbone frameworks as the corresponding hydrates. They are, respectively, monoclinic FePO4, space group P21/n, a= 5.480(1) A, b = 7.480(1) A, c= 8.054(1) A, β = 95.71(1)°, and Z = 4; and orthorhombic FePO4, space group Pbca, a = 9.171(1) A, 9.456(1) A, c = 8.675(1) A, and Z = 8. Both of these phases are thermally unstable relative to the trigonal quartz-like FePO4. The electrochemical studies find that the orthorhombic iron phosphate is more active than the monoclinic phase, while both are more active than trigonal FePO4. Both phases approach Curie−Weiss behavior at room temperature, with t...
159 citations
TL;DR: The phase relationships, crystallography and magnetic phase diagram of the pseudo-binary Gd5Si4-Gd5Ge4 system in the as-cast state is described in this article.
146 citations
TL;DR: In this paper, a large quantity of single-crystal MoO3 nanobelts were synthesized by a low-temperature, simple solution method without using any templates or catalysts.
Abstract: Bulk quantities of single-crystal MoO3 nanobelts were synthesized by a low-temperature, simple solution method without using any templates or catalysts. X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, and energy-dispersive x-ray analysis indicated that as-synthesized nanobelts were pure orthorhombic structured MoO3 grown along [001], with the lengths up to more than 10 μm, width ranging between 50 and 400 nm, and width-to-thickness ratios of about 5 to 20. The possible growth mechanism and the influence factors were reported.
146 citations
TL;DR: In this paper, a simple technique for the preparation of lanthanum ferrite LaFeO 3+d nanopowders by the polymerizable complex (PC) method based on the Pechini-type reaction route was reported.
142 citations
TL;DR: In this paper, the influence of cation order-disorder phenomena on the crystal structure, magnetic and electrical transport properties of new CMR perovskites for LBaMn 2 O 6 - γ (L=Pr, Nd, Sm, Eu, Gd, Tb) series has been investigated.
Abstract: Influence of cation order-disorder phenomena on the crystal structure, magnetic, and electrical transport properties of new CMR perovskites for LBaMn 2 O 6 - γ (L=Pr, Nd, Sm, Eu, Gd, Tb) series has been investigated. For each rare-earth ion three compounds have been synthesized by the topotactic reduction-oxidation method. Structural investigations have shown the oxygen-stoichiometry LBaMn 2 O 6 compound obtained in air to be cubic with disordered L 3 + and Ba 2 + cations whereas the oxygen-deficient LBaMn 2 O 5 is tetragonal with ordered L 3 + and Ba 2 + and alternate stacking of rare earth and barium containing layers along c. This crystal structure is similar to the YBaCuFeO 5 related one. Another form of oxygen-stoichiometry LBaMn 2 O 6 compound obtained by reoxidation of oxygen-deficient LBaMn 2 O 5 is also tetragonal and retains the ordering of L 3 + and Ba 2 + cations. It is notable that the reoxidized EuBaMn 2 O 6 compound has an orthorhombic unit cell. It is observed that this type of cation ordering leads to considerable increase of transition temperature to paramagnetic state. For example, disordered EuBaMn 2 O 6 compound has magnetic properties similar to spin glass and shows freezing temperature of magnetic moments T f 40 K while ordered EuBaMn 2 O 6 is an inhomogeneous ferromagnet with Curie point T C 260 K. Electrical resistivity behavior correlates with magnetization. Below the T C the Pr, Nd, Sm based compounds undergo a transition to metallic state and demonstrate a peak of magnetoresistance. It is supposed that the remarkable changing of the magnetic and electrical properties of the reoxidized compounds is a consequence of the L/Ba ordering and can be explained on the base of the Goodenough-Kanamori rules for 180° indirect superexchange interactions taking into account an ion size effect in A sublattice of perovskite.
141 citations
TL;DR: In this paper, the magnetic entropy change ΔSM of the series of ferromagnetic perovskites La2/3(Ca1−xSrx)1/3MnO3, with x=0, 005, 015, 025, 050, 075 and 1, has been measured near their Curie temperatures.
Abstract: From data of initial magnetization isotherms, the magnetic entropy change ΔSM of the series of ferromagnetic perovskites La2/3(Ca1−xSrx)1/3MnO3, with x=0, 005, 015, 025, 050, 075 and 1, has been measured near their Curie temperatures The results go from 37 J kg−1 K−1 for La2/3Ca1/3MnO3 to 15 J kg−1 K−1 for La2/3Sr1/3MnO3 Nevertheless, the evolution of ΔSM with x is not monotonic, it shows a steep decrease between x=005 and x=015 This point corresponds to a tolerance factor t=092, at which the system changes from orthorhombic (Pbnm) to rhombohedral (R3c) structure, and the magnetic phase transition from first to second order Provided that rhombohedral symmetry forbids static long-range cooperative Jahn–Teller distortions, present in orthorhombic samples, we interpret our results as the strong increase of lattice effects in them The anomalous thermal expansion at the Curie temperature, due to these lattice effects, is thought to underlie the jump in ΔSM with x
TL;DR: A novel Re(I) complex, Re(CO)(3)ClL (L = 2-(1-ethylbenzimidazol-2-yl)pyridine), has been synthesized and structurally characterized by single-crystal X-ray diffraction analysis and confirmed that the Re complex can function as a bright orange-red emitter and an electron transport material in an electroluminescent device.
Abstract: A novel Re(I) complex, Re(CO)3ClL (L = 2-(1-ethylbenzimidazol-2-yl)pyridine), has been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Crystal data for C17H13ClN3O3Re: space group, orthorhombic, Pbca; a = 12.713(6) A; b = 15.103(7) A; c = 18.253(8) A; Z = 8. Stable vacuum vapor deposition of the Re complex has been verified by UV−vis and infrared spectroscopy. A two-layer electroluminescent device with configuration of ITO/TPD/Re(CO)3ClL/Mg0.9Ag0.1/Ag has been fabricated, which gave a turn-on voltage of as low as 3 V and a maximum luminance of 113 cd/m2 at a bias voltage of 10.5 V, and confirmed that the Re complex can function as a bright orange-red emitter and an electron transport material in an electroluminescent device.
TL;DR: In this article, the effect of hydrostatic pressure on the two polymorphs of paracetamol was studied by X-ray diffraction in the diamond anvil cell at pressures up to 4.5 GPa (for the monoclinic form) and up to 5.5 GPs for the orthorhombic form.
Abstract: Effect of hydrostatic pressure on the two (I – monoclinic and II – orthorhombic) polymorphs of paracetamol was studied by X-ray diffraction in the diamond anvil cell at pressures up to 4.5 GPa (for the monoclinic form) and up to 5.5 GPa (for the orthorhombic form). The two groups of phenomena were studied: (i) the anisotropic structural distortion of the same polymorph, (ii) transitions between the polymorphs induced by pressure.
TL;DR: The structures and temperature-dependent photoluminescence properties of the one-dimensional compounds [(TPA(2)Au][Au(CN)(2)], 1, and (TPA)AoCl, 2, are reported and Scanning electron microscopy studies indicate that single crystals of both compounds are noninsulating.
Abstract: The structures and temperature-dependent photoluminescence properties of the one-dimensional compounds [(TPA)(2)Au][Au(CN)(2)], 1, and (TPA)AuCl, 2, are reported An extended linear chain with weak AuAu interactions along the c-axis is evident in the structure of 1, and a helical chain with a pitch of 3271 A is seen for 2 The intrachain AuAu separation is 3457(1) and 3396(2) A in 1 and 2, respectively As a result of this weak AuAu interaction, the physical properties of these compounds are anisotropic Scanning electron microscopy (SEM) studies indicate that single crystals of both compounds are noninsulating Single crystals of 1 do not luminesce visibly, but grinding the crystals finely initiates a strong green emission under UV irradiation at room temperature Further interesting optical properties include the dependence of the emission profile of the powder on the exciting wavelength and luminescence thermochromism When excited at wavelengths < 360 nm, the powder exhibits a blue emission at 425 nm while excitation with longer wavelengths leads to a green emission near 500 nm While the green emission dominates at ambient temperature, cooling to cryogenic temperatures leads to the dominance of the blue emission Fibers of 2 are luminescent at 78 K with an emission band centered at 580 nm Compound 1 crystallizes in the orthorhombic space group Cccm (No 66), with Z = 2, a = 6011(1) A, b = 23877(6) A, c = 6914(1) A, V = 9923(3) A(3), and R = 00337 Compound 2 crystallizes in the trigonal space group R3 (No 148), with Z = 18, a = 22587(2) A, b = 22587(2) A, c = 9814(2) A, V = 4336 A(3), and R = 00283
TL;DR: In this paper, the Raman active phonons in perovskites crystallized in rhombohedral symmetry (LaMnO 3.15 and LaCoO 3) were reported.
TL;DR: In this article, the phase transition between different perovskite-related structures is analyzed in terms of the Gibbs phase rule. But the phase transitions between different structures of a ternary oxide ABO3−−-δ become two-phase regions in a quasi-binary system like ABO 3−−−δ.
Abstract: Oxygen non-stoichiometry, structural properties, and phase relations in Ca and Sr substituted LaMnO3 ± δ were studied by means of thermal analysis, X-ray diffraction, and iodometric titration. Hexagonal α-SrMnO3 − δ and LaMnO3 ± δ perovskite are only partly miscible. Room temperature metastable La1 − xSrxMnO3 ± δ solid solutions, prepared by quenching from high temperatures where there is complete solid solubility between cubic β-SrMnO3 − δ and LaMnO3 ± δ perovskite, have rhombohedral, tetragonal or cubic symmetry dependent on the Sr content. Orthorhombic LaMnO3 + δ and CaMnO3 − δ
form a stable La1 − xCaxMnO3 ± δ solid solution in the whole composition region. The unit cell volume of La1 − xSrxMnO3 ± δ and La1 − xCaxMnO3 ± δ solid solutions is reduced with decreasing La-content mainly due to the correlated change in average oxidation state from Mn3+ to Mn4+. The oxygen stoichiometry changes from cation deficient (oxygen excess) at high La-content to oxygen deficiency at low La-content. The enthalpy of the phase transitions of CaMnO3 − δ and the transition from α-SrMnO3
(hexagonal) to β-SrMnO3 − δ
(perovskite)
were obtained by differential thermal analysis. Finally, the physical appearance of first order phase transition between different perovskite-related structures is analysed in terms of the Gibbs phase rule. First order transitions between different structures of a ternary oxide ABO3 − δ become two-phase regions in a quasi-binary system like ABO3 − δ–A′BO3 − δ.
TL;DR: In this paper, a new oxynitride, LaZrO2N, has been synthesized by the reaction of a highly reactive X-ray amorphous La2Zr2O7 precursor with flowing ammonia at between 900 and 1000 °C.
Abstract: A new oxynitride, LaZrO2N, has been synthesized by the reaction of a highly reactive X-ray amorphous La2Zr2O7 precursor with flowing ammonia at between 900 and 1000 °C. The white insulating material crystallizes in the GdFeO3 distorted perovskite structure type with orthorhombic space group Pnma and with a = 5.875 25(5) A, b = 8.250 31(7) A, c = 5.810 08(5) A, and Z = 4, as determined by neutron powder diffraction. A detailed structural analysis of the isostructural NdTiO2N is also reported: Pnma, a = 5.5492(1) A, b = 7.8017(1) A, c = 5.529 01(9) A, and Z = 4. LaTiO2N crystallizes in a different distorted perovskite structure, which is triclinic, and consequently has two distinct Ti(O4N2) octahedra (LaTiO2N: I1, a = 5.6097(1) A, b = 7.8719(2) A, c = 5.5752(1) A, α = 90.199(2)°, β = 90.154(3)°, γ = 89.988(8)°, Z = 4). Oxide and nitride ions are completely disordered in all three phases. The M(O,N)6 octahedra (M = Ti, Zr) in these phases and a number of perovskite titanates and zirconates become more reg...
TL;DR: The authors showed that oxomolybdate−organic ligand coordination transition-metal fragments can merge their merit to generate some interesting architectures by hydrothermal reaction and synthesize three compounds.
Abstract: Three compounds, [Cu(4,4‘-bpy)]2MoO4·2H2O (1), [Cu(4,4‘-bpy)]2Mo2O7 (2), and [Cu(4,4‘-bpy)(nic)(H2O)]2Mo8O26 (3), are synthesized by hydrothermal reaction, which suggests that oxomolybdate−organic ligand coordination transition-metal fragments can merge their merit to generate some interesting architectures. Crystal data for [Cu(4,4‘-bpy)]2MoO4·2H2O (1): monoclinic system, space group C2/c, a = 10.936(1), b = 17.775(1), and c = 14.484(1) A, β = 110.15(1)°, and Z = 4. Crystal data for [Cu(4,4‘-bpy)]2Mo2O7 (2): orthorhombic system, space group Pbcn, a = 11.841(1), b = 9.105(1), and c = 21.311(1) A, and Z = 4. Crystal data for [Cu(4,4‘-bpy)(nic)(H2O)]2Mo8O26 (3): monoclinic system, space group P2(1)/n, a = 11.457(1), b = 16.918(1), and c = 12.463(1) A, β = 92.6(1)°, and Z = 2. Compound 1 is built up from {MoO4} tetrahedra linking of 4,4‘-bpy coordination copper(I) chain fragments as a railroad-like framework. Compound 2 has noticeable structural features: two {Mo2O7} and four {CuO2N2} tetrahedra are conn...
TL;DR: In this article, the optical and electrical properties of polycrystalline orthorhombic BaSi2 prepared by arc melting in Ar atmosphere were investigated, and it was shown that indirect and direct absorption edges were 1.15 and 1.25 eV, respectively.
Abstract: Optical and electrical properties of polycrystalline orthorhombic BaSi2 prepared by arc melting in Ar atmosphere were investigated. The optical absorption spectra measured at room temperature showed that indirect and direct absorption edges were 1.15 and 1.25 eV, respectively. The activation energy estimated from temperature dependence of the resistivity was 1.10 eV. These results agreed well with a calculated band structure of the orthorhombic BaSi2 by first principles calculation using density functional theory.
TL;DR: In this article, the structure of WO3 was studied in fine temperature steps, from room temperature to 1000 °C, by means of very high-resolution neutron powder diffraction, and it was confirmed that the sample used was single-phase monoclinic in space group P21/n at room temperature.
Abstract: The structures of tungsten trioxide, WO3, have been studied in fine temperature steps, from room temperature to 1000 °C, by means of very high-resolution neutron powder diffraction. It was confirmed that the sample used was single-phase monoclinic in space group P21/n at room temperature. In addition to this monoclinic structure, the structures observed were an orthorhombic structure in Pbcn from about 350 to 720 °C, another monoclinic structure in P21/c from about 720 to 800 °C, a tetragonal structure in space group P4/ncc from 800 to 900 °C, and above 900 °C a second tetragonal structure in P4/nmm. The transformation from the Pbcn orthorhombic to the P21/c monoclinic structure was certainly discontinuous, and indeed just above 720 °C two-phase mixtures were observed. The other transitions were continuous or nearly so, all three being apparently tricritical in nature. The sequence of phases, and nature (continuous or otherwise) of the transitions between them, can be well understood by reference to the results from a group theoretical analysis.
TL;DR: In this paper, the lattice constants, c/a axial ratios, and cell volumes indicate continuous changes from orthorhombic to cubic through a tetragonal phase.
Abstract: Structure refinements of solid solutions of (Ca 1 - x Sr x )TiO 3 (x = 0.0, 0.25, 0.5, 0.6, 0.65, and 1.0) were undertaken using single crystals at ambient conditions. Their lattice constants, c/a axial ratios, and cell volumes indicate continuous changes from orthorhombic to cubic through a tetragonal phase. The orthorhombic structure is continuous between x = 0.0 and x = 0.6, and a phase at x = 0.65 shows a tetragonal structure with space group I4/mcm. With increasing Sr substitution, the symmetry changes to cubic with Pm3m space group. A-O and B-O distances in ABO 3 perovskite were determined as a function of the composition of the A cation (Ca and Sr). Tilting and rotation angles of the TiO 6 octahedral linkage with x of (Ca 1 - x Sr x )TiO 3 were also evaluated. Single-crystal structure refinements of Ca 0 . 3 5 Sr 0 . 6 5 TiO 3 perovskite at 3.5, 4.1, and 7.0 GPa at 300 K were carried out using a diamond anvil cell. The tetragonal phase transforms to an orthorhombic structure with space group Pbnm at 3.5 GPa. The polymorphic transition of V I I I A 2 + V I B 4 + O 3 perovskites under compression is discussed.
TL;DR: In this article, the absorption spectrum of ferrosilite (FeSiO3) was investigated in the infrared region and it was shown that the Mg end members have sharp and characteristic features in the far-IR region and in particular that it is easy to distinguish the two types of crystalline structures in this wavelength range.
Abstract: Crystalline Mg-Fe pyroxenes with dierent Mg=(Mg+ Fe) ratio (MgSiO3 Mg0:5Fe0:5SiO3 and FeSiO3 )w ere synthesized in laboratory and their absorption properties were investigated in the infrared region. The absorption spectrum of ferrosilite (FeSiO3) is reported for the first time in this work. Our study confirmed that the Mg end members have sharp and characteristic features in the far-IR region and in particular that it is easy to distinguish the two types of crystalline structures (orthorhombic and monoclinic) in this wavelength range. In addition we find that the absorption spectra depend on the chemistry and crystal structure of the material: (1) The far-IR features which are prominent in the Mg end members, vanish when the iron concentration is increased. However, even in the iron bearing pyroxenes, the variation of the mid-IR features with Fe concentration is less significant in comparison to that of the far-IR features. (2) Peak positions shifted to longer wavelength an increase in iron concentration; the dependence of the shift is approximately linear in wavenumber (cm 1 ). (3) Bandwidths of the far-IR bands for the end members are significantly smaller than those of solid solutions. These results suggest that the far-IR features of pyroxenes are very sensitive to chemical composition and crystal structure. Therefore, far-IR features are a very useful constraint on the chemical composition and crystal structure of circumstellar pyroxenes.
TL;DR: In this article, the authors used the Landau-Ginzburg-Devonshire approach to calculate the longitudinal piezoelectric coefficient in an arbitrary direction, d33*(θ), as a function of temperature in tetragonal BaTiO3 crystals.
Abstract: Using the Landau–Ginzburg–Devonshire approach, the longitudinal piezoelectric coefficient in an arbitrary direction, d33*(θ), was calculated as a function of temperature in tetragonal BaTiO3 crystals. The direction along which d33*(θ) is maximum is a function of piezoelectric dij coefficients referred to the crystallographic coordinate system. Below a critical ratio of the shear and longitudinal coefficients, d15/d33, the maximum d33*(θ) lies along the [001] axis. As the low-temperature orthorhombic phase is approached on cooling, the d15 increases, reflecting softening of the lattice along the axis of the incipient orthorhombic distortion, and the direction of maximum d33*(θ) deviates significantly from the [001] axis. Our results suggest that the enhanced d33*(θ) coefficient along a direction other than the polar axis recently reported in some ferroelectrics is at least in part controlled by these intrinsic lattice effects.
TL;DR: In this article, the electric field induced polarization and strain properties of 0.7Pb(Mg1/3Nb2/3)O3−0.3PbTiO3 crystals have been investigated under both unipolar and bipolar drive.
Abstract: The electric-field induced polarization (P–E) and strain (e–E) characteristics of 〈110〉c-oriented 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 crystals have been investigated, under both unipolar and bipolar drive. A field-induced transformation was observed below saturation. Under unipolar drive, the P–E and e–E loops were anhysteretic even at the transformation point, demonstrating complete reversibility between ferroelectric rhombohedral and orthorhombic phases. The results show that “polarization rotation” can occur between 〈111〉c and 〈110〉c, where the polarization is confined to the (100)c in a monoclinic Mb type symmetry.
TL;DR: In this paper, a controlled synthesis of transition metal complexes with mixed ligands has led to two new compounds with the same empirical formula [Fe(N3)2(4,4′-bpy)] (4, 4′ bpy = 4, 4 4′- bipyridine).
Abstract: Controlled synthesis of transition metal complexes with mixed ligands has led to two new compounds with the same empirical formula [Fe(N3)2(4,4′-bpy)] (4,4′-bpy=4,4′- bipyridine). The compound 2D-[Fe(N3)2(4,4′-bpy)] (I) contains end-on (EO) bridging azido ligands. It crystallizes in the orthorhombic crystal system, space group Cmmm (No. 65): a=11.444(2) A, b=15.181(3) A, c=3.458(1) A, V=600.8(2) A3, and Z=2. The compound 3D-[Fe(N3)2(4,4′-bpy)] (II) contains end-to-end (EE) azido bridges. It belongs to the tetragonal crystal system, space group P41212 (No. 92): a=8.132(1) A, b=8.132(1) A, c=16.708(3) A, V=1104.9(5) A3, and Z=4. Crystals of I and II have been grown by the diffusion method. Phase-pure samples of both compounds have been obtained by means of an optimal solution synthesis. Spontaneous long-range magnetic ordering was found in both I and II, with I being a metamagnet, and II being a ferromagnet. For I, in the low-field region, multiple transitions at TN1=20 K and TN2=5 K were observed, and these indicated the existence of Fe moment reorientation. Heat capacity measurements on II confirmed ferromagnetic transition at TC=20 K.
TL;DR: In this article, the synthesis of LaNi 1− x Mn x O 3+ δ samples with different oxygen contents was carried out by X-ray and neutron powder diffraction.
TL;DR: The fabrication and electro-optical properties of liquid-crystal-filled polymer photonic crystals of orthorhombic F symmetry, which exhibit electrically switchable Bragg diffraction at ~8-10 V/microm with crystal structure in good agreement with theoretical expectations are reported.
Abstract: Electrically switchable photonic crystals are simply and rapidly formed by holographic polymerization-induced phase separation of liquid crystal from a monomer-liquid crystal mixture. We report the fabrication and electro-optical properties of liquid-crystal-filled polymer photonic crystals of orthorhombic F symmetry. Inverse opal and fcc structures can also be obtained. The crystals exhibit electrically switchable Bragg diffraction at ~8-10 V/microm with crystal structure in good agreement with theoretical expectations. These photonic crystals compare favorably with liquid-crystal-imbibed colloidal crystal arrays.
TL;DR: To lower the hydrogen desorption temperature of Mg(2)NiH(4), it is suggested to destabilize this compound by introducing defects in the counterion matrix surrounding the tetrahedral Ni(0)H( 4)(4)(4-) complexes.
Abstract: Structural stability and bonding properties of the hydrogen storage material Mg2NiH4 (monoclinic, C2/c, Z = 8) were investigated and compared to those of Ba2PdH4 (orthorhombic, Pnma, Z = 8) using ab initio density functional calculations. Both compounds belong to the family of complex transition metal hydrides. Their crystal structures contain discrete tetrahedral 18 electron complexes T0H44- (T = Ni, Pd). However, the bonding situation in the two systems was found to be quite different. For Ba2PdH4, the electronic density of states mirrors perfectly the molecular states of the complex PdH44-, whereas for Mg2NiH4 a clear relation between molecular states of TH44- and the density of states of the solid-state compound is missing. Differences in bonding of Ba2PdH4 and Mg2NiH4 originate in the different strength of the T−H interactions (Pd−H interactions are considerably stronger than Ni−H ones) and in the different strength of the interaction between the alkaline-earth metal component and H (Ba−H interaction...
TL;DR: In this article, the structure of low-temperature β-Ta2O5 oxide has been studied by the method of Rietveld full-profile analysis, and it is established that this oxide has an orthorhombic structure with lattice parameters a = 6.217 A, b=3.677 A, and c = 7.794 A.
Abstract: The structure of low-temperature β-Ta2O5 oxide has been studied by the method of Rietveld full-profile analysis. It is established that this oxide has an orthorhombic structure with lattice parameters a = 6.217 A, b=3.677 A, and c = 7.794 A. The atomic coordinates and thermal parameters are also determined.
TL;DR: In-situ neutron and X-ray diffraction experiments were used to determine the crystal structure of Ba 2 In 2 O 5 as related to temperature as discussed by the authors, which is a Brownmillerite-type crystal structure from room temperature to 900 °C.