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1.
采用高温固相反应合成了M5-2xSmxNax(PO4)3F(M=Ca,Sr,Ba)荧光体,研究了其在真空紫外-可见光范围的发光特性。发现在Ca5(PO4)3F中Sm3+的电荷迁移带约在191 nm,在Sr5(PO4)3F中约在199 nm,而在Ba5(PO4)3F中约在204 nm,随着被取代碱土离子半径的增大电荷迁移能量逐渐减小。比较了M5(PO4)3F (M=Ca,Sr,Ba)中Sm3+和Eu3+电荷迁移能量的关系。  相似文献   

2.
Evolution of hydrogen during thermal decomposition of some MIIHPO3 (M= Mg, Ca, Zn, Sr, Cd, Ba) phosphities under nitrogen atmosphere was investigated. Step mechanism of thermal decomposition has been proposed.
Zusammenfassung Es wurde die Wasserstoffentwicklung während der thermischen Zersetzung einiger Phosphite MII)HPO3 (mitM=Mg, Ca, Zn, Sr, Cd, Ba) in einer Stickstoffatmosphäre untersucht. Es wurde ein schematischer Mechanismus für die thermische Zersetzungsreaktion gegeben.
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3.
Structural and photoluminescence properties of undoped and Ce3+-doped novel silicon-oxynitride phosphors of Ba4−zMzSi8O20−3xN2x (M=Mg, Sr, Ca) are reported. Single-phase solid solutions of Ba4−zMzSi8O20−3xN2x oxynitride were synthesized by partial substitutions of 3O2−→2N3− and Ba→M (M=Mg, Ca, Sr) in orthorhombic Ba2Si4O10. The influences of the type of alkaline earth ions of M, the Ce3+ concentration on the photoluminescence properties and thermal quenching behaviors of Ba3MSi8O20−3xN2x (M=Mg, Ca, Sr, x=0.5) were investigated. Under excitation at about 330 nm, Ba3MSi8O20−3xN2x:Ce3+ (x=0.5) exhibits efficient blue emission centered at 400-450 nm in the range of 350-650 nm owing to the 5d→4f transition of Ce3+. The emission band of Ce3+ shifts to long wavelength by increasing the ionic size of M due to the modification of the crystal field, as well as the Ce3+ concentrations due to the Stokes shift and energy transfer or reabsorption of Ce3+ ions. Among the silicon-oxynitride phosphors of Ba3MSi8O18.5N:Ce3+, M=Sr0.6Ca0.4 possesses the best thermal stability probably related to its high onset of the absorption edge of Ce3+.  相似文献   

4.
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   

5.
The degradation of the hydrates of the alkaline earth thioferratesM(FeS2)2·xH2O,M=Ca, Sr, Ba, resulting from ion exchange on KFeS2, is studied by TG and by X-ray diffraction analysis. The zeolitic character of the very loosely bound water in these compounds is proved. There exist several cristallographically distinct phases as a function of the water content.
Herrn Prof. Dr.O. Hoffmann-Ostenhof zum 65. Geburtstag gewidmet.  相似文献   

6.
The thermal decompositions of anhydrous fluorosilicates M2SiF6 (M=Li, Na, K, Rb, Cs) and MSiF6 (M=Ca, Sr, Ba) were investigated. The decompositions proceeded according to a simple acid-base mechanism with evolution of SiF4. The influence of the cationic counter-ion acidity (expressed by means of the electronegativity force) on the course of thermal decomposition was estimated quantitatively.  相似文献   

7.
The systems CaHPO4−MHPO4−H2O (M=Sr, Ba) were studied at 50°C. ForM=Sr, the series of single phases, Ca1−xSrxHPO4 for 0.95<X<0.75 and CaxSr1−xHPO4 for 0.4<X<1 have been prepared. These solid solution were caracterized by their infrared spectra and their crystallographic unit cell parameters. ForM=Ba a new phase Ca2Ba(HPO4)3 has been determined. It was characterized by DRX, IR, ATD and chemical analyses.

Zusammenfassung Bei 50°C wurde das System CaHPO4−MHPO4−H2O (mitM=Sr, Ba) untersucht. FürM=Sr wurden Serien von Einzelphasen erhalten: Ca1−xSrxHPO4 für 0.95<X< 0.75 und CaxSr1−xHPO4 für 0.4<X<1. Diese Mischkristalle wurden anhand ihrer Infrarotspektren und ihrer kristallographischen Elementarzellenparameter charakterisiert. FürM=Ba wurde die neue Phase Ca2Ba(HPO4)3 ermittelt. Sie wurde mittels DRX, IR, ATD und chemischer Analyse charakterisiert.
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8.
The thermal decomposition of anhydrous fluoroborates MBF4 (M=Li, Na, K, Rb, Cs) and M(BF4)2 (M=Ca, Sr, Ba) was investigated. The decomposition proceeds according to a simple acid-base mechanism with evolution of BF3. The influence of the acidity of cationic counterions, expressed by the electronegativity force on the course of thermal decomposition was estimated quantitatively.  相似文献   

9.
Ternary metal oxynitrides are generally prepared by heating the corresponding metal oxides with ammonia for long durations at high temperatures. In order to find a simple route that avoids use of gaseous ammonia, we have employed urea as the nitriding agent. In this method, ternary metal oxynitrides are obtained by heating the corresponding metal carbonates and transition metal oxides with excess urea. By this route, ternary metal oxynitrides of the formulae MTaO2N (M=Ca, Sr or Ba), MNbO2N (M=Sr or Ba), LaTiO2N and SrMoO3−xNx have been prepared successfully. The oxynitrides so obtained were generally in the form of nanoparticles, and were characterized by various physical techniques.  相似文献   

10.
Pressure, temperature, and composition phase equilibrium diagrams of new solid solution systems of the Cd1?xMxS (M = Mg, Ca, Sr) type were investigated using the quenching method. The stable region for the rock-salt-type phase is widely extended toward the high-temperature/low-pressure region by substituting 10–20 mole% of Cd with Ca or Sr. Temperature and composition phase diagrams for each solid solution system were obtained at 2 GPa. The rock-salt-type phase stability is discussed in view of these phase relations.  相似文献   

11.
It is well known that the manganites-based solid solutions are interesting for their electric and magnetic properties. LaMnO3 exhibits a distorted perovskite structure due to Mn3+ ion, which determines the presence of the Jahn–Teller effect. Replacing La3+ host ions by cations of lower valence leads to the disappearance of this effect and changes the characteristics of these materials. Although the formation of manganites-based solid solutions has been intensively studied, there are some unelucidated aspects concerning their formation mechanism, depending both on the precursors used and on the thermal treatment applied in order to obtain suitable properties. In this work the formation mechanism of La0.7M0.3MnO3 (M=Ca, Sr, Ca+Sr in equimolecular mixture) solid solutions, in isothermal and non-isothermal conditions, was studied. For this purpose XRD, DTA/TG and spectral techniques were used. The solid solutions formation was found to be more dependent on the Mn-precursors type than the thermal treatment conditions. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

12.
An improved method for the synthesis of four heterotrinuclearpolyacids of the type: Hx[EM′yM″zO40nH2O (E=P, Si; M′=Mo, W; M″=V, W) was elaborated. The studied compounds were characterized by elemental analysis, IR spectra and thermal behaviour over 20–800°C temperature range. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

13.
The compounds BiMO2NO3, with M=Pb, Ca, Sr, and Ba, were obtained as single-phase products from solid-state reactions in an atmosphere of nitrous gases. The oxide nitrates with Pb and Ca crystallize in the tetragonal space group I4/mmm with two formula units per unit cell; the oxide nitrates with Sr and Ba crystallize in the orthorhombic space group Cmmm with four formula units per unit cell. Lattice parameters at room temperature are a=397.199(4), c=1482.57(2) pm for M=Pb; a=396.337(5), c=1412.83(3) pm for M=Ca; a=1448.76(3), b=567.62(1), c=582.40(1) pm for M=Sr and a=1536.50(8), b=571.67(3), c=597.55(3) pm for M=Ba. The structures, which were refined by powder X-ray diffraction, consist of alternating [BiMO2]+ and [NO3] layers stacked along the direction of the long axis. IR and thermogravimetric data are also given. The various M2+ cations in BiMO2NO3 are compatible with each other; therefore and because of their layer-type structure, these compounds are interesting precursors for oxide materials, e.g., the HTSC compounds (Bi,Pb)2Sr2Can−1CunOx.  相似文献   

14.
The infrared spectra of orthoarsenates with apatite structure, of the formulaM 5(AsO4)3 X (M=Ca, Sr, Ba, Pb andX=F, Cl,Br) are measured and interpreted on the basis of a site-symmetry analysis. The influence of the different cations on the internal vibrations of the AsO3 4-ions is discussed.
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15.
Differential thermal analysis was used to detect the onset and extent of the catalytic oxidation of 1% hexane and to a lesser extent 3% CO in air. Unsupported catalysts as ground single crystals and in polycrystaline form were selected principally from the system La1?xMxMnO3 where M = Pb. Ca, Sr, and Ba; although other materials, also having the perovskite structure, were investigated. The catalytic activity of these previously reported materials was confirmed. In general, catalytic activity followed the order Ba~Sr~Ca>Pb. Work ov2r a wide range of x in the Pb system did not indicate a strong variation with x. CO proved easier to oxidize than hexane but generally exhibited similar trends. An acid etch was found to enhance the activity and the effect of subsequent reheating was studied. Catalysts prepared by a variety of techniques were compared.  相似文献   

16.
The light absorption of the phases occurring in the systemsMF2/NiF2 (M=Ba, Sr, Ca) has been investigated. The colour curves of Ba2NiF6 (I) and of BaNiF4 (II) show characteristic differences. The colour curve of SrNiF4 is similar to that of II. The colour curves of the system CaF2/NiF2 are compared with those of the system CaF2/CoF2. From the colour curve of the latter system one can unambiguously infer that mixed cristals Ca1–x Co x F2 (x0,01) exist. No evidence could be found for the existence of mixed cristals Ca1–x Ni x F2 by the spectrophtometric method.

Mit 6 Abbildungen  相似文献   

17.
In order to clarify the effect of PbO addition on the formation steps of the superconducting phases in the system Bi2O3?SrO?CaO?CuO, a study of solid-state reactions under non-isothermal conditions, in the PbO?MO (M=Ca, Sr, Ca+Sr) system has been carried out. Results suggest that the reactivity of the components in the system containing PbO and CaO is much higher than in the system containing SrO. The Ca2PbO4 compound is formed first even in the system whereM=Ca+Sr. It is confirmed that Ca2PbO4 systems containing PbO.  相似文献   

18.
ZnS(1-x)MSx(x=0.01 and M=Mn2+, Cu2+ and Eu2+) compounds have been obtained by precipitation from homogeneous solutions of zinc, copper, manganese and europium salts, with S2- as the precipitating anion, formed by the decomposition of thioacetamide. The thermal study of the milled zinc acetate, thioacetamide, copper acetate, manganese acetate and europium nitrate, respectively, was studied for thermal analyis TG/DSC. XRD respect exhibits a zinc blend crystal structure. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

19.
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   

20.
《Solid State Sciences》2007,9(5):404-409
Laser zone melting was employed in this work to prepare MTiO3 based coatings over commercial, polycrystalline Al2O3 substrates, using the corresponding mixtures of powdered alkaline earth carbonates and TiO2 as starting materials. In situ synthesis of the series M = Ca, Sr, Ba was studied using a CO2 laser as the heating source, emitting at 10.6 μm, following substrate preheating to a temperature of 750 °C and sample displacement speed of 500 mm h−1. Microstructure (SEM) and phase composition (XRD) demonstrated in situ formation of crystalline MTiO3 perovskite (M = Ca, Sr), MAl2O4 (M = Ca), MAl12O19 magnetoplumbite type (M = Sr) and MAl14O22 β-alumina type (M = Ba) phases. Substantial interaction with the substrate resulted in stable, 50–150 μm thick, composite coatings.  相似文献   

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