Crystal structure of α‴-(Zn1−x Cd x )3As2 (x = 0.26)

Single crystals of the α?-phase of (Zn_{1 ? x} Cd _x )₃As₂ solid solution (x = 0.26) have been prepared and investigated by X-ray diffraction analysis. The tetragonal unit-cell parameters are found to be a = b = 8.5377(2) Å, c = 24.0666(9) Å, sp. gr. I4₁/amd, Z = 16. Zn and Cd atoms in the crystal statistically occupy three symmetrically independent positions in the mirror planes and are tetrahedrally coordinated by arsenic atoms. (Zn,Cd) tetrahedra share edges to form a three-dimensional structure framework. The α?-phase is geometrically related to the fluorite structure. The character of arrangement of tetrahedral vacancies in fluorite-like unit cells is revealed. Chains of tetrahedral vacancies form microchannels oriented parallel the a and b axes, which pierce the three-dimensional structure framework at different levels along the c axis. The structure of α″-Cd₃As₂ crystals is found to be similar to that of α?-(Zn_0.74Cd_0.26)₃As₂.     

Optical band gap and Raman spectra in some (Bi2O3)x(WO3)y(TeO2)100−x−y and (PbO)x(WO3)y(TeO2)100−x−y glasses

The glasses representing (Bi₂O₃)_x(WO₃)_y(TeO₂)_100?x?y and (PbO)_x(WO₃)_y(TeO₂)_100?x?y systems were prepared. The dilatometric glass-transition temperatures of examined glass samples were found in the region 383–434 °C, the coefficient of thermal expansion varied from 12 to 16 ppm/°C and the density ranged from 6.30₂ to 6.80₈ g/cm³. From the optical transmission measurements of thin glassy bulk samples prepared by a glass blowing, the optical gap values were found in the narrow region 3.21–3.36 eV. For the temperature interval 300–480 K, the values of the temperature coefficient of the optical band gap varied from 3.7 × 10^?4 to 5.24 × 10^?4 eV/K. It is suggested that Raman feature observed at around 350 cm^?1 can be assigned to an overlap of Raman bands attributed to WO₆ corner shared octahedra and to the following three atomic linkages: Bi–O–Te, Pb–O–Te and W–O–Te.     

CaCu_3Ti_(4+x)O_(12+2x)陶瓷的电学性能

采用传统的固相合成方法在1100℃,保温3 h制备了不同Ti含量的CaCu3Ti4+xO12+2x陶瓷(x=-0.5,-0.2,0,0.2,0.5)。通过XRD分析了CCTO的相组成;在-20~100℃温度范围内、500 Hz~1 MHz的频率范围测量了CaCu3Ti4+xO12+2x陶瓷的介电特性和阻抗特性。Ti的化学计量变化明显的影响了CCTO陶瓷的电学性能,系统对比发现Ti的含量偏离CaCu3Ti4O12的化学计量比,会显著的降低CCTO陶瓷的介电常数,同时增加介电损耗。     

Investigation of the structure and properties of (K x (NH4)1 − x )3H(SO4)2 single crystals

The influence of isomorphous replacement in the cation sublattice on the kinetics of the phase transition in single crystals of the solid solutions (K _x (NH₄)_{1 ? x} ) _m H _n (SO₄)_{(m + n)/2} · yH₂O belonging to the K₃H(SO₄)₂-(NH₄)₃H(SO₄)₂-H₂O salt system was studied. Superproton phase transitions for the end compositions of this system have been found earlier. The optical and thermal properties of crystals with the composition (K,NH₄)₃H(SO₄)₂ in the temperature range from 295 to 500 K were investigated, and the crystal structure was determined at 295 K. The results of the study and the comparison with the literature data show that the replacement of potassium atoms with ammonia leads to a fundamental change in the kinetics of the phase transition, the phase-transition temperature remaining virtually unchanged.     

Electrical properties of glass and liquid semiconductor system (As2Te3)x(Tl2Se)1−x

We have measured the electrical conductivity and thermoelectric power of the pseudobinary system (As₂Te₃)_x(Tl₂Se)_1−x both in the glass and liquid states. The effect of the addition of excess Tl has also been examined. It has been found that the activation energy of electronic conduction is closely related to the average atomization energy of these materials.     

Growth and structure of photosensitive Pb1−x Mn x Te(Ga) epitaxial films

The growth and structure of (1-1.5)-μm-thick Pb_1?x Mn _x Te(Ga)(x = 0.06) films with 0.4?0.9 at % of gallium, grown on BaF₂(111) and Pb_1?x Sn _x Te (x = 0.2) (100) substrates by molecular beam epitaxy, have been investigated. It is established that the films are crystallized into an fcc structure, and their growth planes are (111) and (100), according to the substrate orientation. The optimal conditions for obtaining high-resistivity photosensitive p-and n-type films with a perfect crystal structure (W _1/2 = 80″?100″) have been determined.     

Synthesis and Structure Refinement of Polycrystalline Solid Solution: Na1 + x Zr2 − x Sb x P3O12 (x = 0.1)

Abstract  The solid solution of Na_1 + x Zr_2 − x Sb _x P₃O₁₂ (x = 0.1) was prepared at 1,000 °C by ceramic route. The ceramic material belonging to sodium zirconium phosphate (hereafter NZP) family crystallizes in space group R-3c with unit cell parameters: a = b = 8.77283(16) ?, c = 22.8375(7) ?, α = β = 90.0° γ = 120.0° and Z = 6. The structure of the title phase has been determined by Rietveld refinement of the powder diffraction data on GSAS software. The refinement converges to a satisfactory structure fit with R _p = 0.0764, R _wp = 0.1099 and RF ² = 0.0450. The interatomic distances and bond angles are in good agreement with their standard values. The particle size along prominent reflecting planes ranges between 13 and 50 nm. The polyhedral (ZrO₆ and PO₄ and NaO₈) distortions and valence calculations from bond strength data are also reported. The investigations show that the Sb⁺³ cation occupies the zirconium (A^VI) site of NZP structural framework and resultant charge compensation takes place through partial occupation of M₂ site by Na⁺ ions. Index Abstract  Synthesis and Structure Refinement of Polycrystalline Solid Solution: Na_1 + x Zr _2 −  x Sb _x P ₃ O ₁₂ ( x  = 0.1) O. P. Shrivastava and Rashmi Chourasia Antimony enters crystallochemically in the framework of nano ceramic sodium zirconium phosphate at the Zr site of the ZrO₆ octahedra which are inter linked by PO₄ tetrahedra through corner sharing of the vertical columns. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Sr_xLa_(1-x)MgAl_(11)O_(19-0.5x)热障涂层材料的固相合成

利用固相法在1600℃左右制备出LaMgAl11O19和Sr0.5La0.5MgAl11O18.75片体,研究SrxLa1-xMgAl11O19-0.5x的合成反应过程,掺杂元素Sr对合成过程以及材料微观结构的影响。用X射线衍射仪(XRD)及场发射扫描电镜(SEM)表征材料的相结构和微观形貌。结果表明:合成出的材料皆为单相的具有磁铁铅矿晶型的六铝酸盐,材料是由许多片状小板随机排列而成;Sr降低了该材料的最终生成温度。     

Characterization of an asymmetric M(chelate)2(μ-Cl)2MCl2 dimer and isolation of corresponding DMSO adducts: X-ray crystal structures of Co(phen)2(μ-Cl)2CoCl2⋅C4H8O and M(chelate)Cl2(DMSO) x (Co, x = 1; Ni, x = 2) complexes

In aqueous solution, [M(chelate)Cl₂]x (chelate = 2,2-bipyridine, 1,10-phenanthroline) complexes can disproportionate to produce M(chelate)₂ ⁿ⁺ species that contain two chelating ligands. After extraction with organic solvent,Co(phen)₂(-Cl)₂CoCl₂(1) has been characterized by X-ray diffraction (monoclinic, C2/c, a = 10.278(2)Å, b = 22.026(5)Å, c = 12.941(3)Å, = 103.959(4)°, Z = 4, 2414 reflections [I 2 (I)], R ₁ = 0.0321, wR ₂ = 0.0864). However, addition of [M(chelate)Cl₂]x starting materials to dimethyl sulfoxide produces complexes that retain a single chelate ligand. The pentacoordinate complex Co(bpy)Cl₂DMSO (2) has been structurally characterized (triclinic, P , a = 7.824(2)Å, b = 9.570(4)Å, c = 10.025(2)Å, = 83.24(3)°, = 87.14(2)°, = 83.35(3)°, Z = 2, 2455 reflections [I 2 (I)], R ₁ = 0.0278, wR ₂ = 0.0747). In the case of nickel, two different geometric isomers are observed, depending on the chelate identity: trans-(DMSO)₂Ni(bpy)Cl₂ DMSO (3) (monoclinic, P21/c, a = 10.9149(8)Å, b = 12.1287(9)Å, c = 17.0044(13)Å, = 98.610(1)°, Z = 4,3519 reflections [I 2 (I)], R ₁ = 0.0209, wR ₂ = 0.0560) and cis-(DMSO)₂Ni(phen)Cl₂ (4) (monoclinic, P21/c, a = 8.404(2)Å, b = 14.051(4)Å, c = 16.710(4)Å, = 92.44(3)°, Z = 4, 3069 reflections [I 2 (I)], R ₁ = 0.0691, wR ₂ = 0.1782).     

The AC conductivity of superionic conducting glasses (AgI)x−(Ag4P2O7)1−x (x = 0.8, 0.75, 0.7): Experiment and analysis based on the generalized Langevin equation

The frequency-dependent complex impedance of superionic conducting glasses (AgI)_x − (Ag₄P₂O₇)_1−x (x = 0.3, 0.25, 0.20) was measured from 5 Hz to 500 kHz below room temperature. The frequency dependence of the conductivity and the electric modulus observed here cannot be expressed by a single relaxation equation, but it is well described by an equivalent circuit involving a contribution due to Jonscher's universal law σ [ω] ∼ ωⁿ (0 < n < 1). A linear relation between the DC conductivity and the relaxation time was observed irrespective of the sample compositions. These results are explained on the basis of the generalized Langevin equation associated with a non-exponential memory function. The physical basis of this approach is discussed in terms of the distribution of transition times arising from non-periodic potentials formed by immobile anions and many-body interactions among mobile cations at very high concentration in the superionic conducting glass.     

Magnetic, magnetocaloric, and lattice properties of the La(Fe x Si1 − x )13 ferromagnets

The magnetic and lattice properties of a sample of La(Fe_0.86Si_0.14)₁₃ ferromagnet have been measured. The influence that neutron irradiation has on the physical properties of this ferromagnet is studied. It is shown that the irradiation of this sample by a fluence of 3 × 10¹⁹ n/cm² increases the lattice constant a and the Curie temperature (T _C ) as the volume magnetostriction decreases. A model of ferromagnet is proposed which satisfactorily describes the dependence a(T) of the initial and irradiated samples and their magnetic properties. The temperature dependence of the change in entropy when switching the magnetic field on and off is calculated. It is established that the change in both the magnetic and lattice parts of the total entropy at the magnetic phase transition must be taken into account for La(Fe _x Si_{1 ? x} )₁₃ compounds.     

Local lattice strains in the system of cubic Zn0.999Fe0.001S x Se1 − x (0 ≤ x ≤ 1) crystals

The structure of cubic Zn_0.999Fe_0.001S _x Se_{1 ? x} (0 ≤ x ≤ 1) crystals obtained by vapor-phase chemical transport has been investigated by thermal-neutron diffraction. The diffraction patterns of these crystals are found to exhibit previously unknown diffuse-scattering effects related to local static atomic displacements in the metastable fcc lattice. It is substantiated that the tendency to form polytypes, which is characteristic to a greater extent of zinc sulfide, can be a key factor of instability in the lattice of compounds belonging to the series of anion-substituted solid solutions under study.     

Bulk glassy (Fe0.474Co0.474Nb0.052)100 − x(B0.8Si0.2)x alloys prepared using commercial raw materials

The alloy compositions have been optimized by modifying the B and Si contents in (Fe_0.474Co_0.474Nb_0.052)_100 ? x(B_0.8Si_0.2)_x alloy system with commercial materials. The thermal stability of the supercooled liquid improves with the increased B and Si contents from x = 22 to 28. The composition of the alloy with x = 26 is close to a eutectic point. By copper mold casting, (Fe_0.474Co_0.474Nb_0.052)_100 ? x(B_0.8Si_0.2)_x bulk glassy alloys with diameters up to 5 mm were synthesized for the composition range of x from 22 to 28. In addition to high glass-forming ability (GFA), the (Fe_0.474Co_0.474Nb_0.052)_100 ? x(B_0.8Si_0.2)_x glassy alloys exhibit good soft magnetic properties as well, i.e., rather high saturation magnetization of 0.84–1.07 T, low coercive field of 1.8–3.2 A/m, high initial permeability of 10100–24100 at 1 kHz under a field of 1 A/m and Curie temperature of 620–730 K.     

Crystal structure of cesium sodium hexathiocyanatobismuthate Cs2Na[Bi(SCN)6] and characterization of Cs2Na[Bi(SCN)6−x Cl x ] and Cs2Na[Bi2(SCN)9−x Cl x ] complexes by X-ray powder diffraction

Cs₂Na[Bi(SCN)₆] crystallizes in the trigonal space group with one formal molecule per unit cell.M=846.25,a=7.189(1),c=10.580(2) ,V=473.5(1) ,D _x =2.967 g cm^–3, (MoK)=13.70 mm^–1,F(000)=378. FinalR=0.029 for 917 absorption-corrected reflections. The structure consists of infinite[Bi(SCN)₆Na] ^2– anionic chains along thec axis with slightly distorted octahedral Bi–6S and Na–6N coordination and Cs⁺ ions surrounded by three anionic chains with irregular coordination by six N and three S atoms. X-ray powder diffractograms of three complexes, Cs₂Na[Bi(SCN)_6–x Cl _x ] withx=2, 3 and 4, indicate that the mixed complexes are not isostructural and can be indexed in different orthorombic unit cells witha=14.617(8),b=12.32(1),c=10.769(6) forx=2;a=15.37(1),b=10.81(1),c=10.287(6) forx=3 anda=14.662(7),b=14.366(7),c=7.932(4) forx=4. The two dinuclear complexes Cs₂Na[Bi₂(SCN)_9–x Cl _x ] withx=2 and 3, despite the large similarity of their diffractograms, are not isostructural and can be indexed in different orthorombic unit cells witha=14.79(1),b=13.72(1),c=10.591(5) forx=2 anda=18.423(8),b=15.657(7),c=7.410(7) forx=3.     

The preparation and structural studies in the (80 − x)TeO2–20ZnO–(x)Er2O3 glass system

Er³⁺-doped tellurite glasses of the (80 ? x)TeO₂–20ZnO–(x)Er₂O₃ system (0.5 mol% ? x ? 2.5 mol%) have successfully been made by melt-quenching technique and their structure has been investigated by means of DTA and Raman spectroscopy. The DTA results show the thermal parameters; such as the glass transition temperature (T_g) and crystallization temperature (T_c) were determined. It is found that this system provides a stable and wide glass formation range in which the glass stability around 99–140 °C may be obtained. The Raman spectroscopy used the structural studies in the glass system. Two Raman shift peaks were observed around 640–670 cm^?1 and 720–740 cm^?1, which correspond to the stretching vibration mode of TeO₄ tbp and TeO₃ tp, respectively. It is found that the spectral shift in Raman spectra is depending on the Er₂O₃ content. This evolution is an indication of the changes in the basic unit of the glass structure.     

Nanostructured crystals of fluorite phases Sr1 − x R x F2 + x and their ordering: 9. The defect crystal and real structure of quenched fluorite phases Sr1 − x Ce x F2 + x (x = 0–0.5)

A Sr_0.7Ce_0.3F_2.3 crystal (CaF₂ type, sp. gr. $Fm\bar 3m$ ), obtained by quenching from melt, has been studied for the first time by X-ray diffraction. Fluorine vacancies and interstitial anions are found in the 8c and 32f sites, respectively. The defect ratio in the Sr_0.7Ce_0.3F_2.3 structure corresponds to the tetrahedral cluster configuration of defects {Sr_{4 ? n} Ce _n F₂₆}. The defect structure of quenched (at a rate of ～25 K/min) crystal differs from that of a crystal grown from melt (cooling at a rate of ～3 K/min) by the displacement of some cations (presumably Ce³⁺) along the threefold axis to the 32f site and the anisotropy of thermal vibrations of ions in the cluster core (F _int(32f)3). The concentration dependence of the lattice parameters of quenched Sr_{1 ? x} Ce _x F_{2 + x} phases (x = 0–0.5) is described by a third-order polynomial: a = 5.80009 + 1.166518 × 10^?3 x ? 1.124969 × 10^?5 x ² + 8.258155 × 10^?8 x ³. The compositional dependence of microdistortions is also nonlinear; maximum microdistortions are observed in the SrF₂ crystal. They decrease with an increase in the cerium concentration x to ～ 0.35. The minimum in the range x = 0.30–0.35 correlates with a composition corresponding to the peak (at x ～ 0.29) in the melting curves of the fluorite phase estimated from the phase diagram of the SrF₂-CeF₃ system (the method of thermal analysis).     

(1-4x)NBT-3xKBT-xBT系压电陶瓷电性能研究

采用传统固相法制备了(1-4x)NBT-3xKBT-xBT(x=0.020～0.035)体系压电陶瓷.采用XRD分析发现该体系陶瓷都能形成单一的钙钛矿型固溶体,并在0.025≤x≤0.032范围内具有三方和四方共存结构,为该体系的准同型相界.当x=0.028时,d33=162 pC/N,Qm=203.29,kp=0.234.电滞回线分析表明,(1-4x)NBT-3xKBT-xBT体系陶瓷随着KBT和BT含量的增加具有从铁电体向反铁电体转变的趋势.     

Growth and characterization of lead-free Ba(1−x)CaxTi(1−y)ZryO3 single crystal

A lead-free Ba_(1?x)Ca_xTi_(1?y)Zr_yO₃ (BCZT) single crystal (x=0.08, y=0.26) was grown by the Czochralski (CZ) method in a mixed flux of TiO₂ and ZrO₂. The composition of as-grown BCZT was analyzed by electron probe micro-analysis. The structure, dielectric properties and phase transition were investigated at different temperatures. The X-ray diffraction results confirmed that the structure of the as-grown BCZT crystal was cubic both at 25 °C and 500 °C. The temperature dependence of the dielectric constant and Raman spectra characterization revealed that there was a phase transition from cubic to tetragonal, which happened between 200 K and 250 K. With increasing frequency, the Curie temperature shifted towards high temperature.