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1.
Dong Wook Kim In-Sun Cho Sangwook Lee Tae Hoon Noh Hyun Suk Jung 《Journal of solid state chemistry》2011,184(8):2103-2107
Divalent metal tungstates, MWO4, with wolframite (M=Zn and Mg) and scheelite (M=Ca and Sr) structures were prepared using a conventional solid state reaction method. Their electronic band structures were investigated by a combination of electronic band structure calculations and electrochemical measurements. From these investigations, it was found that the band structures (i.e. band positions and band gaps) of the divalent metal tungstates were significantly influenced by their crystal structural environments, such as the W-O bond length. Their photovoltaic properties were evaluated by applying to the working electrodes for dye-sensitized solar cells. The dye-sensitized solar cells employing the wolframite-structured metal tungstates (ZnWO4 and MgWO4) exhibited better performance than those using the scheelite-structured metal tungstates (CaWO4 and SrWO4), which was attributed to their enhanced electron transfer resulting from their appropriate band positions. 相似文献
2.
The binary and ternary systems M'O(M'CO3)-Nb2O5 and M'O(M'CO3)-MO-Nb2O5, where M'=Ca,Sr and Ba and M=Cu, Ni, Cd, Zn and Pb, were investigated by means of thermal analysis in the temperature range 20–1500°C. The boundaries
of stability of the solid solutions Sr2−xMexNb2O7,Sr2−xMxNb2O7, Sr4−xMxNb2O9 and Sr6−xMxNb2O11 were determined by means of X-ray diffraction, and IR and Raman spectroscopy. The possibility of prognostication of the phase
fields of stable solid solutions by calculation from the diagrams of the ‘comparative electronegativity of atoms vs. tolerance
factor’ was demonstrated. The kinetic parameters of the interactions in theSrCO3+MO+Nb2O5 powder mixtures were established.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
M. A. Tena G. Monrós J. Carda V. Cantavella P. Escribano 《Journal of Sol-Gel Science and Technology》1994,2(1-3):381-385
In this study, Fe
x
Ti1–2x
M
x
O2 (M=Nb, Ta) rutile solid solutions have been synthesized from gels made from Fe(III) acetylacetonate, NbCl5, TaCl5, Ta(V) ethoxide, TiCl4 and Ti(IV) isopropoxide. The results obtained are compared with those obtained by the ceramic method. The solid solutions synthesized from gels were obtained at lower temperatures than these synthesized by the ceramic method. 相似文献
4.
M.E. Villafuerte-Castrejón J.A. Azamar-Barrios P. Bartolo-Pérez 《Journal of solid state chemistry》1998,140(2):755
Two unusual, extensive new solid solutions of LiNbO3and LiTaO3with MnO have been prepared, where 4Mn2+replace a combination of 3Li+and a pentavalent cation: Nb5+or Ta5+. The formulas are Li1−xM1−xMn4xO3, 0<x<0.13, forM=Nb and 0<x<0.23 forM=Ta. The solid solutions were characterized by X-ray powder diffraction and density measurements. The manganese oxidation states were determined by X-ray photoelectron spectroscopy. 相似文献
5.
S. F. Solodovnikov R. F. Klevtsova P. V. Klevtsov 《Journal of Structural Chemistry》1994,35(6):879-889
General principles of arrangement are discussed and analyzed for 13 known structural types (families) of binary molybdates
and tungstates of uni-and bivalent metals, which were classified according to the degree of condensation of M2+On polyhedral and MoO4 tetrahedral constructions. The structural features of some phases correlate with their ferroelectric, ion-conducting, and
luminescent (laser) properties. We suggest crystallochemical criteria and mechanisms of distortion (ferroelectric) phase transitions
in palmierites, langbeinites, and Rb4Mn(MoO4)3 and show the paths of ionic transport in phases with NaCo231(MoO4)3, alluaudite, and Na2Mg5(MoO4)6 structures. On the basis of the analysis performed, we outlined the compounds that are the most promising for the development
of inorganic materials with efficient physical properties.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 6, pp. 145–157, November–December, 1994.
Translated by T. Yudanova 相似文献
6.
The sections Li2MCl4?4xBr4x of the quaternary systems LiCl-LiBr-MCl2-MBr2 with M = Mn, Cd, and Fe were studied by high-temperature X-ray diffraction patterns and DTA and DSC measurements. In the quasibinary lithium manganese halide system complete series of solid solutions exist between the inverse spinels Li2MnCl4 and Li2MnBr4. Li2MnBr4 and solid solutions with x > 0.54 undergo phase transitions to tetragonal spinels at lower temperatures. In the nonquasibinary system with M = Cd, only at temperatures near 400°C a complete series of mixed crystals is formed. At lower temperatures the system is mainly two-phase with rock salt-type Li1?yCd0.5yCl1?xBrx and cadmium chloride-type Cd1?yLi2yCl2?2xBr2x solid solutions in equilibrium. The lithium iron halide system is similar to that of cadmium, but spinel-type Li2FeBr4 does not exist at any temperature. The manganese and cadmium halide spinels and spinel solid solutions undergo phase transitions to NaCl defect structures at elevated temperatures. 相似文献
7.
Bazarov B. G. Fedorov K. N. Bazarova S. T. Bazarova Zh. G. 《Russian Journal of Applied Chemistry》2002,75(6):1026-1028
The temperature dependence of conductivity of molybdates in the systems M2MoO4-AMoO4-Zr(MoO4)2 was studied. The starting molybdates and molybdates of 5 : 1 : 3 and 1 : 1 : 1 compositions, formed in the systems, exhibit mixed conduction, turning ionic at high temperatures. The sharp bends in linear portions of the temperature dependence of conductivity coincide with the temperatures of polymorphic transitions in the corresponding molybdates. 相似文献
8.
Negative thermal expansion in rare earth molybdates 总被引:4,自引:0,他引:4
Negative thermal expansion in rare earth molybdates of A2Mo3O12 family (A=Y, Er, Yb and Lu) is measured by high temperature X-ray diffraction and dilatometry. Rare earth molybdates which are isostructural with the corresponding rare earth tungstates, also exhibit this phenomena attributed to transverse acoustic vibrations. The rare earth molybdates of A2M3O12 family with an orthorhombic structure (A=Y, Er, Yb and Lu) are highly hygroscopic and exhibit negative thermal expansion after the complete removal of water molecules. Axial thermal expansion co-efficient calculated from high temperature X-ray diffraction (RT-1073K) shows rare earth size effect. As the ‘A’ cation decreases in size, the thermal expansion co-efficient along ‘b’ axis and the linear thermal expansion co-efficient become less negative. The thermal expansion behaviour of the tetragonal La2Mo3O12 is also reported to demonstrate the effect of crystal structure. 相似文献
9.
I. A. Gudkova Z. A. Solodovnikova S. F. Solodovnikov E. S. Zolotova N. V. Kuratieva 《Journal of Structural Chemistry》2011,52(6):1063-1069
A subsolidus triangulation of Li2MoO4-Rb2MoO4-MMoO4 (M = Ca, Sr, Pb, Ba) systems is performed. The RbLiMoO4-Rb2M(MoO4)2 (M = Pb, Ba) joins, where 11 mol.% long Rb2M(MoO4)2-based solid solutions are found, are studied in most detail. Ternary molybdates do not form in the systems, which is confirmed
by spontaneous flux crystallization. The α-Rb2Pb(MoO4)2 crystals are obtained and their crystal structure is solved (a = 20.9724(15) ?, b = 12.1261(8) ?, c = 16.1171(10) ?, β = 115.728(13)°, C2/m space group, R = 0.0695, Z = 16), which is a monoclinic superstructure of the palmierite type and has the largest cell volume and the most complex structure
among lead-containing palmierites. One of the MoO6 tetrahedra is orientationally disordered over two sites; lead atoms are shifted from the centers of their coordination polyhedra
to one of their faces and have cn = 6–8; for rubidium cations cn = 10–12. 相似文献
10.
Udo Steiner 《无机化学与普通化学杂志》2005,631(9):1706-1714
On the Chemical Vapor Transport of Ternary Transition Metal‐ and Earth Alkaline Tungstates MWO4 with Chlorine The chemical vapor transport of transition metal tungstates MWO4 (M=Mn, Co, Ni, Cu, Zn, Cd) was investigated in dependence on mean transport temperature (923 K to 1223 K) and amount of transport agent Cl2. All tungstates migrate in a temperature gradient ΔT = 100 K from the region of higher temperature to the lower temperature with migration rates of 0.5 to 8 mg/h depending on experimental conditions. The transport behaviour was determined by continuous measurement of mass change during the transport experiments. The results were compared to thermo chemical calculations and the influence of moisture content discussed in detail. MgWO4 migrates under the influence of Cl2 in a temperature gradient 1273 K to 1173 K (migration rate 0.7 mg/h), CaWO4 and SrWO4 in a temperature gradient 1423 K to 1323 K (migration rate <0.1 mg/h). 相似文献
11.
A. V. Teterskii S. Yu. Stefanovich B. I. Lazoryak D. A. Rusakov 《Russian Journal of Inorganic Chemistry》2007,52(3):308-314
Whitlockite solid solutions Ca9−x
M
x
R(PO4)7 (M = Mg, Zn, Cd; R = Ln, Y) were synthesized as powders and ceramics using solid-phase synthesis. Dielectric investigations
and second harmonic generation (SHG) tests showed that ferroelectric (FE) phase transitions existing in samples with x = 0 change to antiferro-electric (AFE) transitions between two centrosymmetrical phases in samples with x = 1 or 1.5. The calcium-ion solid electrolyte conductivity in Ca9−x
M
x
R(PO4)7 at high temperatures appears either as a result of an antiferroelectric-paraelectric (AFE-PE) phase transition (for x = 1) or as a result of a separate phase transition near 1173 K (for x = 1.5). The appearance of dielectric properties in whitlockites is discussed with reference to the features of their polar
and centrosymmetrical structures.
Original Russian Text ? A.V. Teterskii, S.Yu. Stefanovich, B.I. Lazoryak, D.A. Rusakov, 2007, published in Zhurnal Neorganicheskoi
Khimii, 2007, Vol. 52, No. 3, pp 357–363. 相似文献
12.
B. G. Bazarov R. F. Klevtsova Zh. G. Bazarova S. F. Solodovnikov S. T. Bazarova K. N. Fedorova 《Russian Chemical Bulletin》1999,48(6):1024-1027
The ternary salt systems M2MoO4−AMoO4−Zr(MoO4)2 (M=K, Tl; A=Mg, Mn, Ni, Co, Cu, Zn, Cd) in a sub-solidus region were studied. New ternary molybdates with the M5A0.5Zr1.5(MoO4)6 and MA0.5Zr0.5(MoO4)2 compositions were synthesized by solid-phase reactions in these systems. The crystallographic and thermal characteristics
of the compounds were found. The electrical properties of potassium—manganese—zirconium molybdates were studied.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1036–1039, June, 1999. 相似文献
13.
In the systems Ca3(PO4)2-MSO4 (M = Sr, Ba), the series of single phase Ca21?3xM2xI(PO4)14?2x(SO4)2x with 0<x<0.15 forM=Sr and 0<x<0.1 forM = Ba have been prepared. These solid solutions, respectively strontium phosphosulfate and barium phosphosulfate, are isostructural with anhydrous tricalcium orthophosphate. They have been characterized by their infrared spectra and their crystallographic unit cell parameters. 相似文献
14.
M. I. Pantyukhina A. L. Podkorytov V. M. Zhukovskii 《Russian Journal of Inorganic Chemistry》2010,55(1):103-111
Homogeneous fields of Sr4 − x
M
x
Nb2O9 (M = Cd, Cu, Ni, or Zn) solid solutions were determined using powder X-ray diffraction. Phase fields were plotted proceeding
from the tolerance factor t and electronegativity ratio $
\bar k_A /\bar k_B
$
\bar k_A /\bar k_B
with a satisfactory fit of experimental results. Thermogravimetry was used to establish the major kinetic laws of solid-phase
synthesis (conversion, rate-controlling stage, and effective activation energy) in (4 − x)SrCO3 + xMO + Nb2O5 powdery mixtures. Direct radiometry was used to determine 90Sr, 63Ni, and 65Zn self-diffusion coefficients in solid solutions based on the Sr4Nb2O9 phase. Electrical conductivity was measured as a function of temperature for all Sr4Nb2O9-“M4Nb2O9” samples. The conductivity of Sr4 − x
M
x
Nb2O9 (M = Cd, Cu, Ni, or Zn) solid solutions has a mixed ion-electron character. 相似文献
15.
Electrochemical cells employing La2O3 and CaO doped thoria and CaF2 as solid electrolytes were used to determine the standard Gibbs energies of formation of some tungstates and aluminates of strontium in the range of 1100 to 1400 K. Enthalpies of formation and entropies of Sr3WO6, Sr2WO5, SrWO4, Sr3Al2O6 and SrAl2O4 have been calculated. Concordance of the results from cells with different combinations of electrodes confirms the reliability of the thermodynamic results. 相似文献
16.
G. Sh. Shekhtman E. I. Burmakin N. B. Smirnov N. O. Esina 《Russian Journal of Electrochemistry》2002,38(5):549-553
In the sodium-orthophosphate-based solid solutions in Na3 – 2x
M
x
PO4 systems (M = Cd, Pb), the electroconduction is maximum near the upper concentration boundaries of the single-phase regions: x 0.4 for M = Cd and x 0.25 for M = Pb. The conductivity values at 300°C are 6.25 × 10–3 and 2.5 × 10–3 S/cm, respectively. The conduction of synthesized solid electrolytes has a co-cation nature. Their electric characteristics, inferior to those of the Na3PO4-based solid solutions obtained via heterovalent substitutions of another type, may be a manifestation of an effect similar to the polyalkali effect. 相似文献
17.
N. B. Smirnov E. I. Burmakin B. D. Antonov G. Sh. Shekhtman 《Russian Journal of Electrochemistry》2000,36(7):736-740
Samples of systems (Na
1-x
K
x
)3.8M0.1P2O7 (M = Ca, Sr, Cd; 0 ≤x ≤ 1) are synthesized. It is established that solid solutions with the structure of γ-K4P2O7 form in these systems. At room temperature, the solutions exist atx ≥ 0.7. In the calcium-containing system, they form a continuous series at temperatures exceeding ∼500°C. The co-cation character
of conduction of the solutions is confirmed by measured transport numbers. The concentration dependences of the electroconductivity
and its activation energy point to a polyalkali effect, which decreases with an increase in the M2+ ion radius. Partial conductivities of sodium and potassium cations in the (Na
1-x
K
x
)3.8Ca0.1P2O7 system are calculated and their dependences on the balance between alkali cations in the solid solution are discussed 相似文献
18.
Takai S. Nakanishi T. Tojo T. Kawaji H. Atake T. Esaka T. 《Journal of Thermal Analysis and Calorimetry》2002,69(3):805-811
Heat capacity measurements were carried out on Pb1-xLaxWO4+x/2 (x=0.2) and Pb1-xLa2x/3WO4 (x=0.2, 0.5) solid solutions prepared by sintering and mechanical alloying (MA) methods. For all the solid solutions, sintered
samples showed slightly larger heat capacity around 100 K in comparison with MA samples, which was presumably caused by the
excitation of mobile oxide ion motion. For sintered scheelite-type structured PbWO4s, high-temperature synthesis introduced oxide ion interstitials even for the Pb1-xLa2x/3WO4 system, which resulted in the excess heat capacity at low temperature for excitation. On the other hand, for the samples
prepared by room-temperature MA technique, oxide ion seemed to occupy the regular sites rather than interstitial ones and
excess heat capacities were not observed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
Jiandong Fan Huaijin Zhang Zhengping Wang Wenwei Ge Jiyang Wang 《Frontiers of Chemistry in China》2006,1(3):264-267
The polycrystalline materials of SrWO4 were synthesized by means of a solid phase reaction with analytical purity SrCO3 and WO3 at high temperature. The transparent SrWO4 single crystal with dimension of ϕ 22 mm×40 mm has been successfully grown along a-axis by Czochralski method. X-ray powder diffraction results show that the as-grown SrWO4 single crystal belongs to tetragonal system and I41/a space group. The measured density of SrWO4 is 6.439 g·cm−3 by buoyancy method. The effective segregation coefficients of W and Sr elements in SrWO4 single crystal are close to 1 by the X-ray fluorescence method.
__________
Translated from Journal of Shandong University (Natural Science), 2005, 40(4) (in Chinese) 相似文献
20.
The phase diagrams of the spinel systems Cd1?xCuxCr2S4, Cd1?xCuxCr2Se4, and Mn1?xCuxCr2S4 have been studied on the basis of X-ray powder photographs of quenched samples and high-temperature X-ray diffraction patterns. At room temperature the mutual solid solubilities of the metallic copper and the semiconducting cadmium and manganese spinels are only small (x < 0.05 and >0.95). The interchangeability, however, increases largely with increasing temperature. Complete series of mixed crystals, as in the Zn1?xCuxCr2X4 (X = S, Se) systems, however, are not formed. The solid solutions with x > 0.07 and <0.95, x > 0.095 and <0.90, and x > 0.36 and <0.87, respectively, formed at higher temperatures cannot be quenched to room temperature without decomposition. The unit cell dimensions of the spinel solid solutions studied obviously do not obey Vegard's rule. 相似文献