Variable—Range hopping in Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-K<Subscript>2</Subscript>B<Subscript>4</Subscript>O<Subscript>7</Subscript> glasses

The dc conductivity of the glasses in the Fe₂O₃-Bi₂O₃-K₂B₄O₇ system was studied at temperatures between 223 and 393 K. At temperatures from 300 to 223 K, T^–1/4 (T is temperature) dependence of the conductivity was found, however, both Mott variable-range hopping and Greaves intermediate range hopping models are found to be applicable. Mott and Greaves parameters analysis gave the density of states at Fermi level N (E_F) = 3.13 × 10²⁰–21.01 × 10²⁰ and 1.93 × 10²¹–16.39 × 10²¹ cm^–3eV^–1 at 240 K, respectively. The variable-range hopping conduction occurred in the temperature range T = 300–223 K, since W_D was found to be large (W_D = 0.08–0.14 eV for these glasses) and dominated the conduction at T < 300 K.     

&lt;&lt;标准化法&gt;&gt;应是一部可以操作的法律

《中华人民共和国标准化法》是1988年12月29日第七届全国人大常委会第五次会议正式通过的,1990年4月6日国务院第53号令批准发布了《中华人民共和国标准化法实施条例》,该法及其实施条例的颁布实施,对于发展社会主义市场经济,促进技术进步,改进产品质量,提高社会经济效益,维护国家和人民的利益,发挥了重要的作用。但是,随着社会主义市场经济的不断发展,《标准化法》及其实施条例已难以适应新形势的需要,应予以修订。(一)《标准化法》只规定相应的“法律责任”,而没有具体的罚则,在执法中难以操作。执法人员对于违反《标准化法》的行为,都是依…     

Microstructure and properties of the Ba<Subscript>0.75−x</Subscript>Ca<Subscript>x</Subscript>La<Subscript>0.25</Subscript>Fe<Subscript>11.6</Subscript>Co<Subscript>0.25</Subscript>Ti<Subscript>0.15</Subscript>O<Subscript>19</Subscript> hexaferrites

In the case of Ti⁴⁺ remain unchanged, the Ca²⁺ substituted Ba_0.75?xCa_xLa_0.25Fe_11.6Co_0.25Ti_0.15O₁₉ (0?≤?x?≤?0.05) were prepared by conventional solid-state reaction method at temperature of 1280 °C. A ball-to-power weight ratio of 10:1. Their crystal structure and magnetic properties were mainly investigated. The results show that the single magnetoplumbite phase structure transformed into the multiphase structure. Meanwhile, the small amount of α-Fe₂O₃ phase existed in M-type phase. The micrographs were observed by a field emission scanning electron microscopy (SEM). Vibrating sample magnetometer (VSM) was used to analyze the magnetic properties. The saturation magnetization (M _s ) first increases then decreases when x from 0 to 0.03. But, when x from 0.03 to 0.05, the saturation magnetization (M _s ) first increases then decreases too. The maximum value is at x?=?0.04 (M _s ?=?70.73 emu/g). The value of coercivity (H _c ) first increases then decreases when x from 0 to 0.04. But, the value increased when x from 0.04 to 0.05. The maximum value is at x?=?0.02 (H _c ?=?1691 Oe).     

Phase equilibria in the Tl<Subscript>5</Subscript>Te<Subscript>3</Subscript>–Tl<Subscript>9</Subscript>BiTe<Subscript>6</Subscript>–Tl<Subscript>9</Subscript>TbTe<Subscript>6</Subscript> system

Phase equilibria in the Tl₅Te₃–Tl₉BiTe₆–Tl₉TbTe₆ system have been studied using differential thermal analysis, X-ray diffraction, and microhardness measurements. We have mapped out a number of vertical sections, the 760-K isothermal section of its phase diagram, and projections of its liquidus and solidus surfaces. The composition dependences of lattice parameters and microhardness have been obtained. The system has been shown to contain a continuous series of solid solutions, which crystallize in a tetragonal structure (Tl₅Te₃ type, sp. gr. I4/mcm).     

Enhanced microwave dielectric properties of Ba<Subscript>0.40</Subscript>Sr<Subscript>0.60</Subscript>TiO<Subscript>3</Subscript>–Zr<Subscript>0.80</Subscript>Sn<Subscript>0.20</Subscript>TiO<Subscript>4</Subscript> composite ceramics

The (1−x) Ba_0.40Sr_0.60TiO₃ (BST)−xZr_0.80Sn_0.20TiO₄ (ZST) composite ceramics with x = 10, 20, 30, and 40 wt% were fabricated by conventional solid-state reaction method. With increasing of ZST content, the dielectric constant of composite ceramics was decreased and dielectric loss increases. The effect of ZnO addition to 70 wt% BST–30 wt% ZST composition on the microstructure and dielectric properties was investigated. The improvements in dielectric constant, dielectric loss, and microwave dielectric properties of composite ceramics can be achieved by ZnO addition. The sample with 98 wt% (70 wt% BST–30 wt% ZST)–2 wt%ZnO composition exhibits promising dielectric properties, with dielectric constant, loss tangent and tunability at 4 kV/mm, of 125, 0.0016 and 12%, at 10 kHz and room temperature. At ~2 GHz, it possesses a dielectric constant of 101 and a Q factor of 187, which makes it a good candidate for tunable microwave device applications.     

Phase equilibria in the system “CaAl<Subscript>2</Subscript>Si<Subscript>3</Subscript>O<Subscript>10</Subscript>”-Na<Subscript>2</Subscript>Al<Subscript>2</Subscript>Si<Subscript>3</Subscript>O<Subscript>10</Subscript>-H<Subscript>2</Subscript>O

The phase equilibria in the “CaAl₂Si₃O₁₀”-Na₂Al₂Si₃O₁₀-H₂O system are analyzed using structural and thermal analysis data, and the ideal gonnardite structure is modeled. The results suggest that, to ensure a better correlation with the structures of the zeolites in this series, a new structural model of the gonnardite-based solid solution must be selected, with the structure rotated through 45° about the c axis in the ab plane.     

BaFe<Subscript>12</Subscript>O<Subscript>19</Subscript> films produced from BaFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> heterostructures

BaFe₁₂O₁₉ hexaferrite films have been produced on thermally oxidized single-crystal silicon (SiO₂/Si) substrates by sequential ion-beam sputtering of BaFe₂O₄ and α-Fe₂O₃ targets in an argon-oxygen atmosphere. Their crystal structure has been studied, and the origin of the impurity phases forming during heat treatment has been identified. The results show that heat treatment may lead to the formation of eutectic melts. As a result, the hexaferrite films may contain spherulites.     

Preparation and luminescence properties of Y<Subscript>3−y</Subscript>Al<Subscript>5−x</Subscript>Ga<Subscript>x</Subscript>O<Subscript>12</Subscript>:Ce<Superscript>3+</Superscript><Subscript>y</Subscript> phosphors

Y_3?yAl_5?xGa_xO₁₂:Ce³⁺_y phosphors were prepared by high temperature solid state reaction method. The crystal structures, the influence of Ga³⁺ concentration on the photoluminescence (PL), cathodoluminescence, thermal stability and morphology of the phosphors were studied in detail. The results indicated that diffraction angle of the samples decreased gradually with the increase of Ga³⁺ ions content in XRD pattern. The emission peak of the spectra show a progressive blue-shift, the intensity increased first and then decreased and the optimal Ga³⁺ concentration in Y_2.94Al_5?xGa_xO₁₂:Ce³⁺_0.06 phosphors is x?=?0.75. The critical concentration of Ce³⁺ in YAGG:Ce³⁺ phosphors is affected with the ratio of Ga³⁺ to Al³⁺ and the Y_2.9Al_4.25Ga_0.75O₁₂:Ce³⁺_0.1 phosphor showed the best performance on PL. However, the optimum concentration of Y_3?yAl_5?xGa_xO₁₂:Ce³⁺_y phosphors is x?=?1.5 and y?=?0.04 when they were excited by cathode ray.     

AC Losses in YBCO-Added Bi<Subscript>1.6</Subscript>Pb<Subscript>0.4</Subscript>Sr<Subscript>2</Subscript>Ca<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript><Emphasis Type="Italic">δ</Emphasis></Subscript> Superconductors

The effect of YBCO adding on the superconducting of BPSCCO system with nominal starting composition of (Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O _δ )_1?x(YBCO) _x with x = 0.00?0.10 was studied. The preparation methods used to prepare the samples are the conventional solid-state techniques. From the XRD data, it is observed that the percentage of the Bi-2223 phase increases and Bi-2212 decreases for addition x = 0.02–0.04, respectively. The effect of YBCO addition on the BPSCCO system also has been investigated in term of AC susceptibility study. We have studied the various applied field dependence of the AC susceptibility in polycrystalline samples. The AC susceptibility measurements in the range 0.05 to 2.00 Oe show that as the applied fields increases, the intergranular AC loss peaks move to lower temperature, and also height decreases and width increases. The effect of YBCO addition for the intergranular critical current J _cm, and the presence of weak links that coupled the superconducting grains were defined.     

Investigation of solid solution of ZrP<Subscript>2</Subscript>O<Subscript>7</Subscript>–Sr<Subscript>2</Subscript>P<Subscript>2</Subscript>O<Subscript>7</Subscript>

In this study, ZrP₂O₇ was synthesized by the solid state reaction of ZrO₂ and NH₄H₂PO₄ at 900 °C. Then, in set 1; 10, 5, 1, 0.5, 0.1, 0.05, 0.03% previously prepared Sr₂P₂O₇ were doped into ZrP₂O₇, and Sr₂P₂O₇ slightly affect the unit cell parameter of cubic ZrP₂O₇ (a = 8.248(6)–8.233(8) Å). The reverse of this process was also applied to Sr₂P₂O₇ system (set 2). ZrP₂O₇ changes the unit cell parameters of orthorhombic Sr₂P₂O₇ in between a = 8.909(5)–8.877(5) Å, b = 13.163(3)–13.12(1) Å, and c = 5.403(2)–5.386(4) Å. Analysis of the vibrations of the P₂O ₇ ^4? ion and approximate band assignments for IR and Raman spectra are also reported in this work. Some coincidences in infrared and Raman spectra both sets were found and strong P–O–P bands were observed. Surface morphology, EDX analysis, and thermoluminescence properties of both sets were given the first time in this paper.     

System ZnO ⋅ B<Subscript>2</Subscript>O<Subscript>3</Subscript>-CuO ⋅ B<Subscript>2</Subscript>O<Subscript>3</Subscript>

Differential thermal analysis and x-ray diffraction data indicate that the ZnO B₂O₃-CuO B₂O₃ join of the ternary system CuO-B₂O₃-ZnO is pseudobinary, with eutectic phase relations and a liquid-liquid miscibility gap in the composition range 25–35 mol % CuO.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 339–340.Original Russian Text Copyright © 2005 by Kasumova, Bananyarly.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Stability of the LaCl<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> and LuCl<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> Ions Studied by Mass Spectrometry

The enthalpy stability of the LaCl ₄ ^? and LuCl ₄ ^? ions is assessed using high-temperature mass spectrometry. The enthalpy of Cl^? detachment is determined to be Δ_rH⁰(298.15 K) = 332 ± 10 kJ/mol for LaCl ₄ ^? and 359 ± 10 kJ/mol for LuCl ₄ ^? .     

Formation-decomposition equilibrium of the NpO<Stack><Subscript>2</Subscript><Superscript>+</Superscript></Stack>·UO<Stack><Subscript>2</Subscript><Superscript>2+</Superscript></Stack> complex in chloride melts

The absorption spectra of the NpO ₂ ⁺ (5f ²) ion were examined in the region of the 3H ₅ ← ³ H ₄ magnetic dipole transition (1530–1760 nm) for series of melts with the UO ₂ ²⁺ concentration varied in the opposite directions: (1) NaCl-2CsCl eutectic melt with growing additions of the Cs₂UO₂Cl₄ complex salt and (2) Cs₂UO₂Cl₄ melt with growing additions of the NaCl-2CsCl mixture. Measurements of the integrated intensities of the bands belonging to the NpO ₂ ⁺ ·UO ₂ ²⁺ complex and unbound NpO ₂ ⁺ throughout the UO ₂ ²⁺ concentration range examined (up to 4.4 M in neat Cs₂UO₂Cl₄ melt) and processing of the data obtained in terms of the mass action law showed that the formation-decomposition reaction of the cation-cation complex can be described adequately only using the equation of reaction in the form NpO₂Cl ₄ ^3? + UO₂Cl ₄ ^2? ? {Cl₄ONpO?UO₂Cl₃}^4? = Cl^? (with the equilibrium constant of 1.3±0.1). Thus, the formation of the cationcation complex should be treated as replacement of chloride ion in the equatorial plane of uranyl(VI) by neptunyl(V), rather than as simple addition of UO ₂ ²⁺ to NpO ₂ ⁺ . The reverse reaction, decomposition of the cation-cation complex, consists essentially in replacement of neptunyl(V) by chloride ion.     

Dual relaxation behaviors and large electrostrictive properties of Bi<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript>–Sr<Subscript>0.85</Subscript>Bi<Subscript>0.1</Subscript>TiO<Subscript>3</Subscript> ceramics

Lead-free ceramics (1???x)Bi_0.5Na_0.5TiO₃–xSr_0.85Bi_0.1TiO₃ (BNT–xSBT, x?=?0.4, 0.5, 0.6 and 0.7) were prepared by a solid-state reaction process. Coexistence of ferroelectric relaxation at low temperature and Maxwell–Wagner dielectric relaxation at high temperature was revealed for the first time in this system. Meanwhile, hysteresis-free P–E loops combined with a very high piezoelectric strain coefficient (d₃₃) of 1658 pC/N concurrently with large electrostrictive coefficient Q?=?0.287 m⁴C^?2 were achieved. The ferroelectric relaxor behavior and large electrostrictive strain might be linked to easy reorientation and reversal of ergodic PNRs and the combined effect of Bi off-center position and lone pair electrons.     

Spectroscopic characterisation of local structure in Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses doped with gadolinium

Gadolinium doped bismuth borate glasses containing up to 30 mol% Y₂O₃ were prepared by fast melt quenching method. The effect of yttrium on the local order in 3B₂O₃ · Bi₂O₃ and B₂O₃ · Bi₂O₃ glass matrices, particularly on the bismuth sites, was investigated by infrared (IR) spectroscopy and electron paramagnetic resonance (EPR) of Gd³⁺ ions. The IR results show that the local structure is more ordered in the glass system with higher bismuth content and the progressive addition of yttrium increases the local disorder in both bismuth–borate glass matrices. The EPR results indicate that Gd³⁺ ions occupy both bismuth and yttrium sites and reflect the same structural disorder like that suggested by IR results.     

Thermal expansion and electrical conductivity of La<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>Mn<Subscript>1 − <Emphasis Type="Italic">y</Emphasis></Subscript>Cr<Subscript>y</Subscript>O<Subscript>3</Subscript>

The thermal expansion and electrical conductivity of La_0.7Sr_0.3Mn_{1 ? y} Cr_yO₃ (y = 0, 0.1, 0.3, 0.4) solid solutions have been studied at temperatures from 300 to 1270 K and oxygen partial pressures from 10^?9 to 2.1 × 10⁴ Pa. The solid solutions crystallize in rhombohedral symmetry (sp. gr. R3c). The lattice parameters of La_0.7Sr_0.3Mn_{1 ? y} Cr_yO₃ decrease with increasing chromium content. Doping with chromium reduces the conductivity of lanthanum manganite, without changing the conductivity type. The charge transport in the solid solutions is due to small-polaron hopping. Disproportionation of the 3d transition metals is shown to play a key role in determining the electrical properties of the solid solutions. Partial chromium substitution for manganese reduces the thermal expansion coefficient of the manganite, improving its compatibility with yttria-stabilized zirconia, which is of practical importance.     

Polycrystalline YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−<Emphasis Type="Italic">δ</Emphasis></Subscript> with Nano-sized Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Inclusions

Series of (YBa₂Cu₃O_7−δ )_1−x (Al₂O₃) _x samples have been prepared using solid state reaction method. Various amount of nano-sized Al₂O₃ particles (∼50 nm) were added with (x=0, 0.005, 0.01, 0.02, and 0.05). The microstructure and the morphology of the polycrystalline samples have been characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The magneto-transport properties of these samples were investigated using resistance–temperature (R–T) and current–voltage (I–V) characteristics. All samples showed an orthorhombic structure with a tendency to transformation to tetragonal phase at higher levels of nanoparticles addition. The morphology of the surface of pure samples reveals a considerable number of weak-links, randomly oriented and clean grain boundaries. While in samples with nano inclusions, grain boundaries were filled with nanosized particle and have less number of weak-links. Significant enhancement of the superconducting critical current density J _c in applied magnetic field was observed due to nano Al₂O₃ inclusions. However, further increase in the value of x decreases the transition temperature T _c and the critical current density J _c . These results were interpreted in terms of the flux pinning mechanisms in granular superconducting networks which leads to a better basic understanding of the performance of YBCO system in high applied magnetic fields.