Quaternary system Li2MoO4-Na2MoO4-CaMoO4-BaMoO4

The Li₂MoO₄-Na₂MoO₄-CaMoO₄-BaMoO₄ quaternary system was studied by differential thermal analysis and direct visual observation. Three invariant points, two peritectic and one eutectic, were located.     

The spinels CoRh2O4 and Co2RhO4

Polycrystalline CoRh₂O₄ and Co₂RhO₄ are cubic, spinel-type double oxides, S.G. Fd3m (No. 227), Z = 8. For CoRh₂O₄, $\text{a}\text{= 8.4992(1)}\text{A}\text{?}$, $\text{U = 613.95(3)}\text{A}\text{?}{}^3$, D_X = 7.11 Mgm^?3, $\text{x}\text{= 0.257}$, Co in 8(a) positions, R = 0.043. For Co₂RhO₄, $\text{a}\text{= 8.299(2)}\text{A}\text{?}$, $\text{U = 517.6(5)}\text{A}\text{?}{}^3$. D_X = 6.62 Mgm^?3, $\text{x}\text{= 0.261}$, half the Co content in 8(a) positions, R = 0.041. IR absorption band frequencies for both spinels are included.     

Liquidus relations in the Li2WO4-Na2WO4-CaWO4 system

Phase relations in the Li₂WO₄-Na₂WO₄-CaWO₄ system were studied by physicochemical analysis. The liquidus surface was mapped out, and the compositions and temperatures of invariant points were determined.     

Electrical transport in the system Li2SO4-mLi2MoO4-2mLi3VO4

The measurement of electrical conductivity () and thermoelectric power (S) of three compounds (namelym = 0, 0.5 and 1) in the system Li₂SO₄-mLi₂moO₄-2mLi₃VO₄ has been reported from 500 ° C to melting point of each solid. All the three solids show superionic phase just below their melting point. In this phase a value decreases but activation energy and span of superionic phase increases for compounds with largerm. Further the phase transition temperature (T _p ) from normal to superionic phase decreases withm. BelowT _p the order of is reversed, it increases withm but in all cases it becomes mixed with dominant ionic part.     

Synthesis and Properties of Zn2TiO4–Zn2SnO4–ZnFe2O4 Solid Solutions

Zn₂TiO₄–Zn₂SnO₄–ZnFe₂O₄ mixed oxides are prepared by low-temperature hydrogen–oxygen plasma synthesis and solid-state reactions. Zn_{2 – x} (Ti _a Sn _b )_{1 – x} Fe_2x O₄ (a+ b = 1, x = 0–1.0) solid solutions are shown to have an inverted cubic spinel structure (sp. gr. Fd3m). The lattice parameter, electrical conductivity, band gap, and molar polarizability of about 100 samples are determined. With increasing Fe content, the lattice parameter, degree of spinel inversion, density, activation energy, and polarizability of the solid solutions decrease, while their conductivity rises.     

Structures des composes CdTm2S4 et CdYb2S4

The structures of CdTm₂S₄ and CdYb₂S₄ were refined in order to establidh the exact cationic distribution. The R factors are 0.037 for 104 reflections (CdTm₂S₄) and 0.039 for 98 reflections (CdYb₂S₄) Unlike CdHo₂S₄ abd CdY₂S₄, the structures are of normal spinel type and intersticial cation defects are not observed.     

Synthesis and characterization of Na2Pb2Pr2W2Ti4Ta4O30

A new complex oxide (Na₂Pb₂Pr₂W₂Ti₄Ta₄O₃₀) of tungsten bronze structural family has been synthesized by a high-temperature solid-state reaction (mixed-oxide) route at 1,050 °C. Room temperature structural analysis shows the formation of a single phase new compound. Study of microstructure of the pellet sample, recorded by scanning electron microscope, exhibits the uniform distribution of different size and shape of grains (with a few small voids) on the surface of the sample. Detailed studies of dielectric properties as a function of frequency and temperature show a dielectric anomaly above room temperature suggesting the existence of a ferroelectric phase transition in the material. Impedance spectroscopic analysis and electrical conductivity of the material exhibit a strong correlation between microstructure and electrical parameters. The temperature dependence of dc conductivity of the compound follows Arrhenius equation. The frequency and temperature dependence of ac conductivity (with fittings) shows the signature of Jonscher’s universal power law. The existence of non-exponential-type of conductivity relaxation in the compound was confirmed.     

Large-scale growth of Cu2ZnSnSe4 and Cu2ZnSnSe4/Cu2ZnSnS4 core/shell nanowires

We present a fast and simple protocol for large-scale preparation of quaternary Cu(2)ZnSnSe(4) (CZTSe), as well as CZTSe/Cu(2)ZnSnS(4) (CZTS) core/shell nanowires using CuSe nanowire bundles as self-sacrificial templates. CuSe nanowire bundles were synthesized by reacting Cu(2 - x)Se nanowire bundles with sodium citrate solution. CZTSe nanowires were prepared by reacting CuSe nanowire bundles with Zn(CH(3)COO)(2) and SnCl(2) in triethylene glycol. X-ray diffraction (XRD) and selected area electron diffraction studies show that stannite CZTSe is formed. The formed CZTSe nanowire bundles have diameters of 200-400 nm and lengths of up to hundreds of micrometers. CZTSe/CZTS nanocable bundles with similar morphologies were grown by the addition of some elemental sulfur to the reaction system for growth of CZTSe bundles. The stannite CZTSe/kesterite CZTS core/shell structure of the grown nanocables was confirmed by XRD and high-resolution transmission electron microscope investigation. The influence of S/Se molar ratio in the reaction system on the crystallographic structures and optical properties of CZTSe/CZTS nanocables was studied. The obtained CZTSe/CZTS core/shell nanocable bundles show broad and enhanced optical absorption over the visible and near-infrared region, which is promising for use in photovoltaic applications.     

硫酸-草酸混合法硬质阳极氧化溶液的分析

1　前　言　　混合酸阳极氧化法是指用含有两种或以上的无机酸或有机酸的混合水溶液对工件进行的阳极氧化。它适用于硬质氧化膜和自然着色法的有机酸电解着色 ,与单一酸阳极氧化法相比有如下优点 :(1)在 10～ 2 0℃下电解 ,能获得耐磨性好的氧化膜和高着色率 ;(2 )实行高电流密度的混合酸电解 ,可防止氧化膜溶解 ,并可在较高温度下有效地形成硬质氧化膜 ;(3)可在较高的温度下实施 ,降低生产成本 ,有利于生产。该法获得的膜层的性能与溶液的成分密切相关 ,因而要求对溶液实行监控分析。然而 ,目前的分析基本上都是沿用单一酸电解液法进行 ,其…     

Nucleation studies in supersaturated aqueous solutions of (NH4)H2PO4 doped with (NH4)2C2O4·H2O

Induction periods were measured for various supersaturated aqueous solutions of ammonium dihydrogen orthophosphate doped with ammounium oxalate monohydrate by the direct vision method. Various critical nucleation parameters were calculated based on classical theory for homogeneous crystal nucleation and the results reported and discussed. The critical nucleation parameters increased with increase in doping concentration.     

Dielectric properties of K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3

Dielectric constant (ɛ), dielectric loss (tan δ) and conductivity (σ) for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ have been measured over the frequency range 100 Hz — 100 kHz and in temperature range 30°C — 400°C. The values of static dielectric constant at room temperature are 7.67 and 4.80 for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively. The plots of log σ against reciprocal temperature at different frequencies of these samples merge into a straight line beyond 250°C and the activation energies calculated in this region are found to be 0.67 eV and 1.98 eV for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively.     

Double phase transitions in K2Pb2Sm2W2Ti4Nb4O30 ferroelectrics

This paper reports about the double phase transition (at 315 and 366 °C) in the polycrystalline sample of K₂Pb₂Sm₂W₂Ti₄Nb₄O₃₀ prepared by a high-temperature solid-state reaction technique. The calcination temperature was decided based on thermogravimetry analysis. Room temperature X-ray structural analysis confirms the formation of a single phase compound. The surface morphology recorded by scanning electron microscope exhibits a uniform grain distribution with high density. Detailed studies on the nature of variation (1) of dielectric parameters with temperature, and (2) polarization with temperature confirmed the existence of ferroelectricity in the material at room temperature. The temperature dependence of dc conductivity shows a typical Arrhenius behavior. The frequency dependence of ac conductivity suggests that the material obeys Jonscher’s universal power law. The variation of current with temperature shows that the material has high pyroelectric co-efficient and figure of merit, thus making it useful for pyroelectric sensors.     

X-ray diffraction study of the CuCr2O4-NiFe2O4 system

Phase relations in the Cu_1-xNi_xCr_2(1-x) solid-solution system, containing Jahn-Teller active cations, were studied by powder x-ray diffraction. The solid solutions with jc > 0.5 were found to have a cubic NiFe₂O₄ (Fd3m) structure. In the range 0.1 <x < 0.4, a cubic phase of approximate composition Cu_0.6Ni_0.4Cr_1.2Fe_0.8O₄ was shown to coexist with a tetragonal phase of composition Cu_0.9Cr_1.2Fe_0.2O₄. The results were interpreted under the assumption that the degree of inversion of the spinel phase varies significantly across the morphotropic region. The lattice parameters and degree of inversion of the solid solutions were determined as a function of composition. The distributions of the divalent and trivalent cations over tetrahedral and octahedral sites were tentatively assessed.     

Magnetic Properties of Nanocrystalline CoFe2O4/ZnFe2O4 Bilayers

Nanocrystalline spinel CoFe₂O₄/ZnFe₂O₄ bilayers were deposited by the pulsed laser deposition technique on amorphous fused quartz substrate at different substrate temperatures ranging from room temperature to 750?°C. The magnetic properties of the bilayers and of the single layer films deposited in identical conditions were studied at 300?K and at 10?K. Magnetic properties of the bilayers, in general, were found to be in between the individual values of the single layers. Magnetic measurements at 10?K clearly showed a two stepped magnetic hysteresis loop corresponding to the switching of the magnetic moments of the soft ZnFe₂O₄ and the hard CoFe₂O₄ layers. A study was also carried out by changing the thickness of ZnFe₂O₄ layer in the bilayer. This study showed that the magnetic properties of the bilayers even at room temperature can be controlled to some extent by changing the thickness of the soft ZnFe₂O₄ layer while maintaining a low substrate temperature of 350?°C.     

Phase equilibria in the Tl2MoO4-Pr2(MoO4)3-Hf(MoO4)2 system and crystal structure of TlPr(MoO4)2

Subsolidus (450–480°C) phase relations in the Tl₂MoO₄-Pr₂(MoO₄)₃-Hf(MoO₄)₂ system have been studied by X-ray diffraction. The system has been shown to contain molybdates with the compositions Tl₅PrHf(MoO₄)₆ (5: 1: 2), TlPrHf_0.5(MoO₄)₃ (1: 1: 1), and Tl₂PrHf₂(MoO₄)_6.5 (2: 1: 4). Single crystals of the double molybdate TlPr(MoO₄)₂ have been grown for the first time from high-temperature solutions through spontaneous nucleation, and their crystal structure has been determined: tetragonal symmetry, sp. gr. P4/nnc, a = 6.3170(1) Å, c = 9.5529(2) Å, V = 381.204(12) ų, Z = 2.     

Ceramics Based on CaSO4⋅2H2O Powder Synthesized from Ca(NO3)2 and (NH4)2SO4

Inorganic Materials - Ceramics consisting of anhydrous calcium sulfate, CaSO4, after firing in the range 800–1000°C have been prepared from calcium sulfate dihydrate (CaSO4?2H2O)...