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Showing papers on "Lattice constant published in 2004"


Journal ArticleDOI
TL;DR: In this article, the crystal structure of compounds with the general formula AB 2 X 4, which crystallize with the same atomic structure as the mineral spinel, MgAl 2 O 4, is reviewed.
Abstract: This paper reviews the crystal structure of compounds with the general formula AB 2 X 4 , which crystallize with the same atomic structure as the mineral spinel, MgAl 2 O 4 . Three degrees of freedom associated with the detailed atomic arrangements of spinels are considered here: (i) the lattice parameter, a; (ii) the anion parameter, u; and (iii) the cation inversion parameter, i. Oxide spinels are used as examples to explore the interrelationships between these parameters.

914 citations


Journal ArticleDOI
TL;DR: In this article, a triangular lattice photonic crystal is formed by dry etching into the top GaN layer, and the chosen lattice spacing causes Bragg scattering of guided modes out of the LED, increasing the extraction efficiency.
Abstract: Electrical operation of InGaN/GaN quantum-well heterostructure photonic crystal light-emitting diodes (PXLEDs) is demonstrated. A triangular lattice photonic crystal is formed by dry etching into the top GaN layer. Light absorption from the metal contact is minimized because the top GaN layers are engineered to provide lateral current spreading, allowing carrier recombination proximal to the photonic crystal yet displaced from the metal contact. The chosen lattice spacing for the photonic crystal causes Bragg scattering of guided modes out of the LED, increasing the extraction efficiency. The far-field radiation patterns of the PXLEDs are heavily modified and display increased radiance, up to ∼1.5 times brighter compared to similar LEDs without the photonic crystal.

395 citations


Journal ArticleDOI
TL;DR: In this article, the optical structure of a representative diatom, Coscinodiscus granii, was analyzed and it was shown that light can be coupled into the waveguide and that there are some photonic resonances in the visible spectral range.
Abstract: We present an analysis of the optical structure of a representative diatom, Coscinodiscus granii. The silica cell wall can be regarded as a photonic crystal slab waveguide with moderate refractive-index contrast. In a cell, at least two different patterns are found: a hexagonal array of pores with a large lattice constant in the valve, and a square array of holes with a small lattice constant in the girdle. It is demonstrated that light can be coupled into the waveguide and that there are some photonic resonances in the visible spectral range, which have been determined by band-structure calculations.

330 citations


Journal ArticleDOI
TL;DR: In this article, a comparative study of as-prepared Pt−Ni alloy catalysts with different Pt/Ni atomic composition was performed using X-ray diffraction spectroscopy at wide angles (WAXS) and Debye function analysis (DFA).
Abstract: Vulcan XC-72 carbon-supported Pt−Ni alloy nanoparticle catalysts with different Pt/Ni atomic composition were prepared via the carbonyl complex route and their structure was studied by X-ray diffraction spectroscopy at wide angles (WAXS) and Debye function analysis (DFA). The very good agreement between the WAXS pattern and DFA simulation revealed that all the as-prepared Pt−Ni alloy catalysts have a unique and highly disordered face-centered cubic structure (solid solution) and that the lattice parameter decreases with the increase of the Ni content in the alloys. Transmission electron microscopy (TEM) images indicated that the as-prepared Pt−Ni alloy nanoparticles were well dispersed on the surface of the carbon support with a narrow particle size distribution and that their mean particle size slightly decreased with the increase in Ni content. Energy-dispersive X-ray analysis (EDX) confirmed that the catalyst composition was nearly the same as that of the nominal value. Thus, a comparative study was ma...

303 citations


Journal ArticleDOI
TL;DR: In this article, the crystal structure of ferromagnetic near-stoichiometric Ni2MnGa alloys with different compositions has been studied at ambient temperature and the range of the average number of valence electrons per atom was determined for phases 5M, 7M, and nonmodulated martensite.
Abstract: The crystal structure of ferromagnetic near-stoichiometric Ni2MnGa alloys with different compositions has been studied at ambient temperature. The studied alloys, with five-layered (5M) and seven-layered (7M) martensitic phases, exhibit the martensitic transformation temperature (TM) up to 353 K. Alloys with these crystal structures are the best candidates for magnetic-field-induced strain applications. The range of the average number of valence electrons per atom (e/a) was determined for phases 5M, 7M, and nonmodulated martensite. Furthermore, a correlation between the martensitic crystal structure, TM and e/a has been established. The lattice parameters ratio (c/a) as a function of e/a or TM has been obtained at ambient temperature for all martensitic phases. That the paramagnetic-ferromagnetic transition influences the structural phase transformation in the Ni–Mn–Ga system has been confirmed.

299 citations


Journal ArticleDOI
TL;DR: In this paper, the lattice constants of pure and Mg doped ZnO thin films were investigated using an x-ray diffractometer (XRD) to investigate the structural properties of the thin films, and the peak position of (002) orientation was found to shift from 34.39° to 34.55°.
Abstract: Pure and Mg doped ZnO thin films were deposited at 400 °C on glass substrates by pulsed laser deposition. An x-ray diffractometer (XRD) was used to investigate the structural properties of the thin films. It is found that all the thin films have a preferred (002) orientation. The peak position of (002) orientation is found to shift from 34.39° to 34.55°. The lattice constants of ZnO thin films were also obtained from XRD data. It is found that, with the increase of the dopant concentration, the lattice constant a decreases from 3.25 to 3.23 A, and c decreases from 5.20 to 5.16 A. From the spectrophotometer transmittance data, the band gap energies of the thin films were calculated by a linear fitting process. The band gap energy of Mg doped ZnO thin film increases with increasing dopant concentration. In photoluminescence (PL) spectra, two PL emission peaks are found in pure ZnO thin films, one is the near band edge (NBE) emission at 3.28 eV, and the other is green-yellow-red emission at around 2.4 eV. However, with the increase of the dopants, no green-yellow-red emissions are found in PL of Mg doped ZnO thin films. The NBE emission has a blueshift compared with that of pure ZnO thin film (as much as 0.12 eV). As time goes on, NBE emission in pure ZnO thin film is enhanced, and the green-yellow-red emissions disappear.

276 citations


Journal ArticleDOI
TL;DR: In this article, the effects of deposition pressure on their crystal structure and multiferroic properties have been investigated at room temperature, showing that the surface roughness and grain size of the films depend dramatically on oxygen pressure.
Abstract: BiFeO3 thin films have been prepared on Pt∕TiO2∕SiO2∕Si substrates under various oxygen pressures of 0.15–0.005Torr at a temperature of 450°C by pulsed-laser deposition. The effects of deposition pressure on their crystal structure and multiferroic properties have been investigated at room temperature. X-ray diffraction analysis (θ-2θ scans and 2-dimensional scans) shows that the BiFeO3 thin films consist of perovskite single phase with tetragonal crystal structure and space group P4mm. The c-axis lattice constant decreases (4.062–4.006A) and c∕a ratio of the films decreases from 1.032 to 1.014 with a decrease in the oxygen pressure. The surface roughness and grain size of the films depend dramatically on oxygen pressures. The dielectric constant of the films decreases with decreasing oxygen pressure. The film deposited at 0.05Torr shows a stable current density and well-saturated hysteresis loop with twice the remanent polarization (2Pr) of 136μC∕cm2 and coercive field (2Ec) of 109kV∕cm. The BiFeO3 thin ...

255 citations


Journal ArticleDOI
TL;DR: In this paper, a series of ZnO1−xSx films with 0.1.0 was deposited by radio-frequency reactive sputtering on different substrates and the structural characterization by x-ray diffraction measurements revealed that the films have wurtzite symmetry and correlated investigations of the layer composition by photoelectron spectroscopy showed that the lattice constant varies linearly with x.
Abstract: A series of ZnO1−xSx films with 0⩽x⩽1.0 was deposited by radio-frequency reactive sputtering on different substrates. The structural characterization by x-ray diffraction measurements revealed that the films have wurtzite symmetry and correlated investigations of the layer composition by photoelectron spectroscopy showed that the lattice constant varies linearly with x. The composition dependence of the band gap energy in the ternary system was determined by optical transmission and the optical bowing parameter was found to be about 3eV.

240 citations


Journal ArticleDOI
TL;DR: Li et al. as discussed by the authors studied the first cycle characteristics of Li[Ni1/3Co 1/3Mn 1 /3]O2 charged up to 4.7 ǫ.

212 citations


Journal ArticleDOI
TL;DR: In this article, the structural, energetic, and adhesion properties of both solid and liquid Al/alpha-Al2O3 interfaces were investigated using a reactive force field (ReaxFF).
Abstract: Using a reactive force field (ReaxFF), we investigated the structural, energetic, and adhesion properties, of both solid and liquid Al/alpha-Al2O3 interfaces. The ReaxFF was developed solely with ab initio calculations on various phases of Al and Al2O3 and Al-O-H clusters. Our computed lattice constants, elastic constants, surface energies, and calculated work of separation for the solid-solid interface agree well with earlier first-principles calculations and experiments. For the liquid-solid system, we also investigated the nonwetting-wetting transition of liquid Al on alpha-Al2O3(0001). Our results revealed that the evaporation of Al atoms and diffusion of O atoms in alpha-Al2O3 lead to the wetting of liquid Al on the oxide surface. The driving force for this process is a decrease in interfacial energy. The nonwetting-wetting transition was found to lie in the 1000–1100 K range, which is in good agreement with sessile drop experiments.

194 citations


Journal ArticleDOI
Chengbao Jiang1, Yousaf Muhammad1, Lifeng Deng1, Wei Wu1, Huibin Xu1 
TL;DR: The Mn-rich Ni50Mn25+xGa25−x (x=0-5) alloys were developed to investigate the structural transitions and magnetic properties.

Journal ArticleDOI
TL;DR: In this paper, the structural phase transformations of 07Pb(Mg1∕3Nb2∕ 3)O3-03PbTiO3 (PMN-30%PT) have been studied using x-ray diffraction (XRD) and neutron scattering as a function of temperature and electric field.
Abstract: The structural phase transformations of 07Pb(Mg1∕3Nb2∕3)O3-03PbTiO3 (PMN-30%PT) have been studied using x-ray diffraction (XRD) and neutron scattering as a function of temperature and electric field We observe the phase transformational sequence (i) cubic (C)→ tetragonal (T)→ rhombohedral (R) in the zero-field-cooled (ZFC) condition; (ii) C→T→ monoclinic (MC)→ monoclinic (MA) in the field-cooled (FC) condition; and (iii) R→MA→MC→T with increasing field at fixed temperature beginning from the ZFC condition Upon removal of the field, the MA phase is stable at room temperature in the FC condition, and also in the ZFC condition with increasing field Several subtleties of our findings are discussed based on results from thermal expansion and dielectric measurements, including (i) the stability of the MA phase, (ii) a difference in lattice parameters between inside bulk and outside layer regions, and (iii) a difference in the phase transition temperature between XRD and dielectric data

Journal ArticleDOI
TL;DR: Zinc oxide powders were heated in different atmospheres at 800 and 1400 °C, and it was found that the value of c0 in crystal structure affected the antibacterial activity of zinc oxide.
Abstract: Zinc oxide powders were heated in different atmospheres at 800 and 1400 degrees C, of which the characterization and the antibacterial activity were studied by X-ray diffractometry and the measurement of the change in electrical conductivity with bacterial growth. The diffraction peaks corresponding to zinc oxide with hexagonal type structure were detected in all samples, which shifted in low-angle side with the increase in the oxidizability of atmosphere during heat-treatment. From the results of calculating lattice constants, a0 and c0, it was found that the value of c0 in hexagonal structure increased with the increase in the oxidizability of atmosphere. On the samples heated at 1400 degrees C, the changes of the c0 value were less than those at 800 degrees C. However, no change of the a0 value showed, irrespective of atmosphere and temperature. Hydrogen peroxide that contributes to the occurrence of antibacterial activity was found to generate from all samples, and the generation amount increased with the increase of c0 value; incidently the amount in the samples heated at 1400 degrees C was less than that at 800 degrees C. The antibacterial activity of zinc oxide increased with the increase of c0 value; that is, it was found that the value of c0 in crystal structure affected the antibacterial activity of zinc oxide.

Journal ArticleDOI
TL;DR: Combined experimental and theoretical analysis of the shifts, with particle size, of core-level binding energies (BE's) of metal nanoparticles on insulating supports, shows that these shifts have an important initial state contribution arising, in large part, because of lattice strain.
Abstract: Our combined experimental and theoretical analysis of the shifts, with particle size, of core-level binding energies (BE's) of metal nanoparticles on insulating supports, shows that these shifts have an important initial state contribution arising, in large part, because of lattice strain. This contribution of BE shifts has not been recognized previously. Lattice strain changes the chemical bonding between the metal atoms and this change induces BE shifts.

Journal ArticleDOI
TL;DR: In this article, the thermal behavior and molecular interaction of a new type of bacterial copolyester, poly(3-hydroxybutyrate-co-3hydroxyhexanoate), P(HB co-HHx) (HHx = 12 mol %), was investigated by using wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC).
Abstract: The thermal behavior and molecular interaction of a new type of bacterial copolyester, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), P(HB-co-HHx) (HHx = 12 mol %), was investigated by using wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The WAXD measurements were carried out over a temperature range from 25 to 110 °C in the scattering angle range of 2θ = 5−13°. The WAXD pattern at room temperature shows that the P(HB-co-HHx) copolymer has an orthorhombic system (α = β = γ = 90°) with a = 5.76 A, b = 13.20 A, and c = 5.96 A (fiber repeat), which is identical to the crystal system of poly(3-hydroxybutyrate) (PHB) homopolymer. However, temperature-dependent variations in the lattice parameters, a and b, of P(HB-co-HHx) are quite different from those of PHB. Only the a lattice parameter increases with temperature, while the b lattice parameter changes very little in the case of crystalline P(HB-co-HHx). It seems that the intermolecular and intramolecular interactions between...

Journal ArticleDOI
TL;DR: In this paper, three parameters which are microstrain, lattice parameter and crystallite size, obtained from X-ray diffraction line profile analysis, were used in a complementary way to study the precipitation/dissolution of various intermetallics and carbides in nickel base superalloy Inconel 625, without extracting the precipitates from the matrix.

Journal ArticleDOI
TL;DR: The structural and electrical properties of magnesium-substituted nickel ferrite having the general formula of Ni1−xMgxFe2O4 have been studied as a function of magnesium ion concentration.

01 Jan 2004
TL;DR: The structural and electrical properties of magnesium-substituted nickel ferrite having the general formula of======Ni1xMgxFe2O4 (x=0, 0.6, 09) has been studied as a function of magnesium ion concentration as discussed by the authors.
Abstract: The structural and electrical properties of magnesium-substituted nickel ferrite having the general formula of Ni1xMgxFe2O4 (x=0, 0.3, 0.6, 0.9) has been studied as a function of magnesium ion concentration. The materials have been prepared by citrate gel process using metal nitrate salts as a cation precursors and citric acid as gelating agent. The powder X-ray diffraction pattern confirms fcc structure for the synthesized compound. The variation of lattice parameter and the tetrahedral radius increases with increase in Mg2+ ion concentration. The AC electrical parameters such as dielectric constant (e0) and loss tangent (tan d) for all the systems have been studied as a function of frequency in the range 50 Hz to 10 kHz at room temperature. A maximum DC electrical conductivity of 3.3 S cm-1 was obtained at a temperature of 1000C and a AC electrical conductivity of 10.94106at 10 kHz was observed in the composition x ¼ 0:6 i.e. for Ni0.4Mg0.6Fe2O4 compound which may be due to the maximum Fe2+ concentration in the octahedral sites. The dielectric constant follows the Maxwell’s–Wagner interfacial polarization and the relaxation peaks were observed in the dielectric loss properties. The FTIR spectra show the characteristic peaks of ferrite sample. The morphological features were studied using scanning electron microscope.

Journal ArticleDOI
TL;DR: It is shown that a preference for the formation of magnetic moments, increasing through the alpha-->beta-->gamma phases, explains their position in the ambient pressure phase diagram and their anomalous variation of atomic density.
Abstract: Total energies for the six known polymorphs of plutonium metal have been calculated within spin and orbital polarized density-functional theory as a function of lattice constant. Theoretical equilibrium volumes and bulk moduli correspond well with experimental data and the calculated total energies are consistent with the known phase diagram of Pu. It is shown that a preference for the formation of magnetic moments, increasing through the alpha-->beta-->gamma phases, explains their position in the ambient pressure phase diagram and their anomalous variation of atomic density. A simple model is presented that establishes a relationship between atomic density, crystal symmetry, and magnetic moments which is universally valid for all Pu phases.

Journal ArticleDOI
TL;DR: Photonic quasicrystal lasers with a Penrose lattice that does not possess translational symmetry but has long-range order are fabricated, and coherent lasing action is observed due to the optical feedback from quasiperiodicity.
Abstract: We have fabricated photonic quasicrystal lasers with a Penrose lattice that does not possess translational symmetry but has long-range order, and observed coherent lasing action due to the optical feedback from quasiperiodicity, exhibiting a variety of 10-fold-symmetric lasing spot patterns. The lattice constant dependence of lasing frequencies and spot patterns show complicated features very different from photonic crystal/random lasers, and we have quantitatively explained them by considering their reciprocal lattice. Unique diversity of their reciprocal lattice opens up new possibilities for the form of lasers.

Journal ArticleDOI
TL;DR: In this paper, the capacity fading mechanism of spinel manganese oxides was investigated and the percent capacity fade of a number of singly substituted LiMn 2-y-z Ni y Li z O 4 (M = Li, Al, Ti, Co, Ni, and Cu and 0 ≤ y ≤ 0.1) oxides is correlated to the initial lattice parameter, initial Mn valence, degree of menganese dissolution, electrode resistance, irreversible capacity (IRC) loss in the first cycle, and lattice parameters difference Δa between the two
Abstract: With the aim of developing a better understanding of the capacity fading mechanisms of spinel manganese oxides, the percent capacity fade of a number of singly substituted LiMn 2-y M y O 4 (M = Li, Al, Ti, Co. Ni, and Cu and 0 ≤ y ≤ 0.2) and doubly substituted LiMn 2-y-z M y Li z O 4 (M = Al. Ti, Fe, Co, Ni, Cu, and Ga, 0 ≤ y ≤ 0. 1, and 0 ≤ z ≤ 0.1) oxides is correlated to the initial lattice parameter, initial manganese valence, degree of manganese dissolution, electrode resistance, irreversible capacity (IRC) loss in the first cycle, and lattice parameter difference Δa between the two cubic phases formed in the two-phase region during the charge-discharge process. The doubly substituted LiMn 2-y-z Ni y Li z O 4 samples exhibit a combination of superior capacity retention and rate capability with lower IRC compared to LiMn 2 O 4 despite a similar amount of manganese dissolution due to a low Aa and the consequent low microstrain. The samples with a low Δa are also characterized by a lower initial lattice parameter and a higher initial Mn valence of >3.58+ for the as-prepared samples. The percent capacity fade, IRC, and Δa all exhibit a sharp decrease as the initial Mn valence in the as-prepared sample exceeds 3.58+.

Journal ArticleDOI
TL;DR: In this paper, the lattice parameters and crystallographic texture in La, Sr-doped soft lead zirconate titanate ceramics were examined using high-energy synchrotron x-ray diffraction.
Abstract: The lattice parameters and crystallographic texture in La, Sr-doped soft lead zirconate titanate ceramics were examined using high-energy synchrotron x-ray diffraction. The preferred orientations in poled tetragonal and rhombohedral ceramics near the morphotropic phase boundary, caused by ferroelectric domain switching, were determined by monitoring the (002)∕(200) and (111)∕(111¯) intensity ratios, respectively. The lattice strains were also monitored using the {111} and {200} plane spacings in tetragonal and rhombohedral ceramics, respectively. The diffraction experiments were carried out in transmission, enabling the true “bulk” state to be characterized. It was observed that for the tetragonal phase both the lattice spacing d{111} and the intensity ratio R{200} varied linearly as a function of sin2Ψ,Ψ being the angle between the plane normal and the macroscopic polar axis. Similar observations were made for d{200} and R{111} in rhombohedral ceramics. The results are interpreted in terms of the remanen...

Journal ArticleDOI
TL;DR: In this article, the authors used density functional theory and the plane-wave pseudopotential method to predict lattice constants (1.0049-1.0463 nm), atomic coordinates, and bulk moduli (176-205 GPa) that are linearly dependent on the B-site cation radius (0.062-0.072 nm).
Abstract: Isometric pyrochlore, A(2)B(2)O(7), with compositions in the Y-2(Ti,Sn,Zr)(2)O-7 ternary system, are of particular interest because there are dramatic changes in properties, such as ionic conductivity, and response to radiation damage, as a function of disordering of the A- and B-site cations and oxygen vacancies. First-principles calculations using density functional theory and the plane-wave pseudopotential method, predict lattice constants (1.0049-1.0463 nm), atomic coordinates, and bulk moduli (176-205 GPa) that are linearly dependent on the B-site cation radius (0.062-0.072 nm). However, the energetics for the formation of cation-antisite (0-2 eV) and Frenkel-pair (4-11 eV) defects do not correlate with cation size, underscoring the importance of the specific electronic configuration of the B-site cation. The greater degree of covalent bonding between as compared with or results in defect formation energies otherwise unexpected solely due to the radius ratios of the cation species. Y2Sn2O7 shows 2-4 eV greater defect formation energies than otherwise predicted through mean B-site cation sizes. Relaxed calculations on coupled cation-antisite and Frenkel-pair defects show that cation-antisite reactions likely drive the oxygen-Frenkel pair defect formation process that ultimately leads to increased oxygen mobility and completely aperiodic structures. Total charge and partial density of states calculations show strikingly different behavior of oxygen on two different crystallographic positions, emphasizing the need for a full account of the electronic structure.

Journal ArticleDOI
TL;DR: In this article, the bulk electronic and optical properties of indium tin oxide (ITO) were calculated using density functional theory (DFT) and the dependence of the electronic properties of ITO on a variety of parameters such as the tin content, cubic lattice parameter and distance between adjacent tin atoms was investigated.

Journal ArticleDOI
TL;DR: In this article, the lattice microstrains of the nanocrystalline Al solid solution determined from the X-ray diffraction analyses are isotropic along different crystallographic directions and high, exhibiting the same order of magnitude as the ratio of the tensile strength to the elastic modulus of the Al crystal.

Journal ArticleDOI
TL;DR: In this article, the results of an atomistic simulation study on the incorporation of ions of the first series of transition metals (Cr3+, Cr4+, Fe2+, Fe3+, Co2+, Co3+, Ni2+, and Ni3+) in the BaTiO3 lattice are presented and discussed.
Abstract: The results of an atomistic simulation study on the incorporation of ions of the first series of transition metals (Cr3+, Cr4+, Fe2+, Fe3+, Co2+, Co3+, Ni2+, and Ni3+), Y3+, and ions of the lanthanide series (Er3+, Gd3+, Tb3+, Pr3+, Pr4+, and La3+) in the BaTiO3 lattice are presented and discussed. The ions of the transition metals prefer to substitute at the titanium site with oxygen-vacancy compensation. For iron and cobalt, oxidation from the divalent to the trivalent state during incorporation is favored. Nickel and chromium are preferentially incorporated in the valence state 2+ and 3+, respectively. Formation of stable defect pairs with different types of lattice defects is predicted for the transition-metal impurities. For La3+ and Pr3+, substitution occurs at the barium site, whereas Y3+, Tb3+, Gd3+, and Er3+ tend to simultaneous substitution on both cation sites. Formation of dopant–titanium-vacancy pairs is predicted for the rare-earth ions and Y3+. The effect of doping on the lattice parameter of c-BaTiO3 has been studied by a mean-field calculation. Comparison with experimental data confirms the dependence of the preferred substitution site on the ionic radius of the impurity. For dopants with intermediate size (Y3+, Er3+, Tb3+, and Gd3+), the Ba/Ti ratio is important in the incorporation mechanism.

Journal ArticleDOI
TL;DR: In this article, high-quality densely packed hexagonal arrays of Ni nanowires have been prepared by filling self-ordered nanopores in alumina membranes, which have been studied by atomic force, high resolution scanning electron microscopies, Rutherford backscattering, and vibrating sample magnetometer techniques.
Abstract: High-quality densely packed hexagonal arrays of Ni nanowires have been prepared by filling self-ordered nanopores in alumina membranes. Nanowires with different diameter d (18–83 nm) and lattice parameter D (65 and 105 nm) have been studied by atomic force, high resolution scanning electron microscopies, Rutherford backscattering, and vibrating sample magnetometer techniques. Axial loops coercivity and remanence decrease with increasing ratio diameter to lattice parameter, r, until nanowires start to interconnect locally. Additionally, hysteresis of in-plane loops increases with packing factor. In order to interpret the experimental results, multipolar magnetostatic interactions among nanowires with increasing ratio r are considered.

Journal ArticleDOI
TL;DR: In this paper, the second-order optical nonlinearities of fresnoite-type crystals, Ba2TiSi2O8 (BTS), StS, and BTG, have been evaluated by measurements on transparent surface-crystallized glasses consisting of Fresnoite type crystals with the Maker fringe technique.
Abstract: Second-order optical nonlinearities, d33 values, of fresnoite-type crystals, Ba2TiSi2O8 (BTS), Sr2TiSi2O8 (STS), and Ba2TiGe2O8 (BTG), have been evaluated by measurements on transparent surface-crystallized glasses consisting of fresnoite-type crystals with the Maker fringe technique. It is found that all these crystals show large d33 values, i.e., d33=13±2 pm/V for BTS, d33=7.2±0.4 pm/V for STS, and d33=22±3 pm/V for BTG. In particular, it is emphasized that BTG has an extremely large d33 value, comparable to LiNbO3 single crystal. It is clarified that the d33 value of fresnoite-type crystals increases with increasing c/a ratio in the lattice parameters of their structures. It is suggested that the increase in the c/a ratio results in the elongation of TiO5 pyramidal units along the c axis, consequently enhancing spontaneous polarizations in the fresnoite-type structure. Transparent surface-crystallized glasses consisting of fresnoite-type crystals are candidates for nonlinear optical materials.

Journal ArticleDOI
TL;DR: The results show a clear and direct lattice relationship between centrally located AlP particles and the surrounding silicon in the hypoeutectic Al-Si alloy.
Abstract: Aluminium phosphide (AlP) particles are often suggested to be the nucleation site for eutectic silicon in Al-Si alloys, since both the crystal structure and lattice parameter of AlP (crystal structure: cubic F43m; lattice parameter: 5.421 A) are close to that of silicon (cubic Fd3m, 5.431 A), and the melting point is higher than the Al-Si eutectic temperature. However, the crystallographic relationships between AlP particles and the surrounding eutectic silicon are seldom reported due to the difficulty in analysing the AlP particles, which react with water during sample preparation for polishing. In this study, the orientation relationships between AlP and Si are analysed by transmission electron microscopy using focused ion-beam milling for sample preparation to investigate the nucleation mechanism of eutectic silicon on AlP. The results show a clear and direct lattice relationship between centrally located AlP particles and the surrounding silicon in the hypoeutectic Al-Si alloy.

Journal ArticleDOI
H. Baltache1, Rabah Khenata1, M. Sahnoun, M. Driz1, B. Abbar2, B. Bouhafs2 
TL;DR: A theoretical study of structural and electronic properties of MgO, CaO and SrO using the full-potential linearized augmented plane wave method was presented in this paper, where the local density approximation was used for exchange-correlation potentials.
Abstract: A theoretical study of structural and electronic properties of MgO, CaO and SrO is presented using the full-potential linearized augmented plane wave method. In this approach, the local density approximation was used for exchange-correlation potentials. Results are given for lattice constant, bulk modulus and its pressure derivative in both NaCl–(B1) and CsCl–(B2) structures. Band structure, density of states and band gap-pressure coefficients in NaCl–(B1) phase are also given. The results are compared with previous calculations and with experimental measurements.