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1.
Rare earth-substituted lead apatites of the Pb10?2xLnxMx(PO4)6Y2(Ln = La, Nd, Eu, Gd, Dy, and Y: M = Na and K; Y = F and Cl) systems were prepared and studied by X-ray diffraction and infrared methods. The powder patterns of all the compounds show the apatite-like hexagonal structure. Singlecrystal precession data reveal that the space group of the Pb6Ln2Na2(PO4)6F2 compounds is probably while that of Pb6Ln2K2(PO4)6F2 is . Analysis of the ir spectra of substituted Ca, Ba, and Pb compounds show the effect of substituted ions on the spectra and support the assumption that substitution in the Ba and Pb systems is an ordered process. Ordering of the substituted ions in the systems studied is discussed in view of changes in lattice parameters, size conditions, and polarizing properties of the ions. 相似文献
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Use of Nd3+, Eu3+, and Gd3+ as local structural probes allows the determination of the rare earth positions in the NaxSr3?2xLnx(PO4)2 (Ln = La to Tb) and KCaLn(PO4)2 phases (Ln = rare earth). Moreover, a common feature of both series is a particularly high splitting of the excitation and levels of the Gd3+ ions. 相似文献
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G. Engel 《Journal of solid state chemistry》1973,6(2):286-292
The infrared spectra of lead hydroxyapatite Pb10(PO4)6(OH)2, oxyapatite Pb10(PO4)6O, and the lead alkaliapatites Pb8M2(PO4)6 (M = Na, K, Rb, T1) were investigated down to 200 cm?1. There are significant differences between all these spectra. In the hydroxy- and oxyapatite spectrum one band is ascribed to the translational motion of the OH? and O2? ions, respectively. The thermal dependance of the dehydration of hydroxy to oxyapatite was studied by X-ray methods, both compounds forming a solid solution. The heat of decomposition of hydroxyapatite was found to be ΔH = 5 kcal/mole. Moreover, complete miscibilities could be shown to exist in the systems and , respectively. 相似文献
4.
The magnetic interaction in the structural units [Fe2O7]8?, built of two corner-sharing FeO4 tetrahedra, in Na8Fe2O7 () has been studied by magnetic susceptibility measurements (4.2–500 K). An exchange integral of ?37 K is obtained by comparison of the experimental values and the calculated ones using a Heisenberg-Dirac-Van Vleck-type Hamiltonian ? = . The hypothesis of magnetically isolated [Fe2O7]8? groups is corroborated by Mössbauer spectroscopy between 1.5 and 77 K. The susceptibility measurements of the solid solutions Na8Fe2?xMxO7 (M = Al, Ga; 0 ≤ x ≤ 0.2 for Al; 0 ≤ x ≤ 2 for Ga) leads to the same conclusion of the existence of isolated Fe3+Fe3+ pairs in Na8Fe2O7. The type of substitution of Fe by Al or Ga is determined; homonuclear Fe3+Fe3+ and M3+M3+ pairs and heteronuclear Fe3+M3+ pairs are formed. 相似文献
5.
Christopher M. Johnson Mark G. Shilton Arthur T. Howe 《Journal of solid state chemistry》1981,37(1):37-43
We have measured the ionic conductivities of pressed pellets of the layered compounds MUO2PO4 · nH2O, and correlated the results with TGA data. The conductivities (in ohm?1 m?1), at temperatures increasing with decreasing water content over the range 20 to 200°C, were approximately as follows: Li+4H2O, 10?4; Li+, Na+, K+, and NH4+3H2O, 10?4, 10?2, 10?4, and 10?4; H+, Li+, and Na+1.5H2O, 10?2, 10?4, and 10?4; Na+1H2O, 10?5; H+, K+, and NH4+0.5H2O, all 10?5; and H+, Li+, Na+, K+, NH+4, and , 10?5, 10?5, 10?4, 10?5, 10?5, and 10?6. A ring mechanism is proposed to account for the high conductivity found in NaUO2PO4 · 3.1H2O. The accurate TGA data showed that most of the hydrates had water vacancies of the Schottky type, and should be represented as MUO2PO4(A ? x)H2O, where x can be between 0 and 0.3. 相似文献
6.
The magnetic and electric properties of V2O3+x were investigated by measurements of magnetic susceptibility, electrical resistivity, magnetotorque, Mössbauer of doped 57Fe, and NMR of 51V, and the results were compared with those of the (V1?xTix)2O3 system or highly pressured V2O3. The results obtained are as follows: (1) The metallic state shows an antiferromagnetic ordering at TN (x). The value of TN for metallic V2O3, obtained by interpolation to x = 0, shows the coincidence between V2O3+x and the (V1?xTix)2O3 system. (2) Magnetic susceptibility of V2O3+x is expressed as χM(V2O3+x) = (1?x)χM(V3+) + xχM(V4+). χM(V4+) obeys the Curie-Weiss law . (3) In the insulating phase, the electrical resistivity ? is expressed as a common equation: . This implies that the substitution of Ti or nonstoichiometry (V+4 + metal vacancies) has little influence on the carrier mobility (or bandwidth). (4) There is a critical length in the c-axis (? 14.01 Å) where the metal-insulator transition takes place. This suggests that the length of the c-axis plays an important role in the metal-insulator transition of V2O3-related compounds. 相似文献
7.
R. Ibañez A. Garcia C. Fouassier P. Hagenmuller 《Journal of solid state chemistry》1984,53(3):406-414
As a consequence of the weak phonon energies and the low crystal field, several excited states of Nd3+ are emitters in the NaxNdxM1?2xGa2G4 thiogallates (x ≤ 0.5 for M = Ca or Sr and ≤0.2 for M = Ba). The infrared emission is little affected by concentration quenching. NaNdGa4S8 is the first efficient stoichiometric sulfide so far reported. Unlike other sulfides previously investigated, the neodymium thiogallates show an intense excitation band, ascribed to electron transfer from the valence band to states constituted essentially by neodymium orbitals. 相似文献
8.
The excess molar enthalpies HmE{(1 ? x2 ? x3)Al + x2Bi + x3Ga}(I) have been measured between 725 and 1170 K along the sections , 1, and 3, and , 1, and 3, with a high-temperature Calvet calorimeter using both the direct- and indirect-drop methods of mixing; experimental uncertainty is quoted respectively at 6.7 per cent and 9.9 per cent. The equilibrium temperatures confirmed phase boundaries previously determined by potentiometry, d.t.a., and calculation. Extrapolation of the experimental excess molar enthalpies to the limiting binary alloys {(1 ? x2)Al + x2Bi} allows new values for the excess molar enthalpies of these alloys to be proposed. The excess molar enthalpies of the ternary liquid mixtures can be represented correctly using these new values and Bonnier's equation. 相似文献
9.
The LiPO3CeP3O9 and NaPO3CeP3O9 systems have been investigated for the first time by DTA, X-ray diffraction, and infrared spectroscopy. Each system forms a single 1:1 compound. LiCe(PO3)4 melts in a peritectic reaction at 980°C. NaCe(PO3)4 melts incongruently, too, at 865°C. These compounds have a monoclinic unit cell with the parameters: a = 16.415(6), b = 7,042(6), c = 9.772(7)Å; β = 126.03(5)°; Z = 4; space group for LiCe (PO3)4; and a = 9.981(4), b = 13.129(6), c = 7.226(5) Å, β = 89.93(4)°, Z = 4, space group for NaCe(PO3)4. It is established that both compounds are mixed polyphosphates with chain structure of the type |MIIMIIIII (PO3)4|∞MII: alkali metal, MIIIII: rare earth. 相似文献
10.
The crystal structure of Ca6Eu2Na2(PO4)6F2 has been determined by single crystal X-ray diffraction. The unit cell constants are and the space group is . The structure was refined by normal full matrix least squares techniques. The final value of the refinement indicator is R = 0.065, based on 419 reflections.The structure of Ca6Eu2Na2(PO4)6F2 contains disordered cations in both the triangle and column positions. The occupation of the six triangle sites is and and of the four column sites , and . 相似文献
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The perfluoronitrosocycloalkanes, heptafluoronitrosocyclobutane and nonafluoronitrosocyclopentane, are convenient precursors to a family of new perfluorocycloalkyl(aryl) diazenes. With aniline and o-aminobenzamide, FNNH and FNNC(O)NH2 (x = 2,3) are formed. Additionally, heptafluoronitrosocyclobutane gives FNNF and FNNNH2 with 2,3,5,6-tetrafluoroaniline and o-phenylenediamine 相似文献
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The electrical conductivity of sintered specimens of nonstoichiometric CeO2?x was measured as a function of temperature (750–1500°C) and oxygen pressure (1–10?22 atm). The isothermal compositional dependence of the electrical conductivity of CeO2?x was determined by combining recently obtained thermodynamic data, x = x(PO2, T), with the conductivity data. The compositional and temperature dependence of the electrical conductivity may be represented by the expressionover the temperature range 750–1500°C and from x = 0.001 to x = 0.1.This expression was rationalized in terms of the following simple relations for (a) the electron carrier concentrationwhere nCe′Ce is the number of Ce′Ce per cm3 and a0 is the lattice parameter and (b) the electron mobility. 相似文献
17.
We have tried to find the pair of z, h(z) functions most conveniently accounting for the variation of A2 with the molecular wieght, M. The selected z, h(z) pair led to a relation of the type allowing determination of the unperturbed dimensions and the B coefficient characterizing the polymer-solvent interactions. The results obtained with various polymer-solvent pairs are compared to those arising from the Stockmayer-Fixman modified equation. 相似文献
18.
A series of germanate spinels Zn2?x(Ni, Co)xGeO4 has been synthesized and investigated by X-ray diffractometry and infrared spectroscopy. Synthesis at 1200°C leads to cubic phases characterized by an inverse, disordered distribution of Ge and bivalent cations (essentially Ni or Co) over the octahedral sites; however, the presence of some short-range order is suggested by the infrared spectrum. Tempering at an appropriate temperature (between 800 and 900°C, depending on the ratio) leads to tetragonal spinel phases, corresponding to the 1:1 order between Ge and bivalent cation on octahedral sites. The transformation is sluggish and proceeds at a significant rate only in a narrow temperature range, just below the transition temperature. A comparison with the behavior of known inverse, ordered titanate spinels shows that, within the family of inverse II–IV spinels M2IIMIVO4, the ratio of the octahedral cationic radii is one of the factors determining the order-disorder transition temperature, and the importance of the tetragonal distortion. 相似文献
19.
The structure of a crystal was established by X-ray analysis. The solution in the cell of symmetry , with a = 6.6702(5), b = 5.3228(8), c = 8.9091(8) Å, β = 100.546(7)°, Z = 1, has led to R = 0.033 and Rw = 0.036 for 2155 reflections with . This structure can be described as two octahedra-wide ReO3-type slabs connected through “planes” of PO4 tetrahedra. A new structural family KxP2W2nO6n+4 can be foreseen which is closely related to the orthorhombic P4W8O32 and the monoclinic RbxP8W8nO24n+16 series. 相似文献
20.
Paul Poix 《Journal of solid state chemistry》1981,40(2):175-179
The study of K2NiF4 and perovskite structure type by the “method of invariants” leads to the relationship: , where (A-X)9 and (A-X)12 are the invariant values associated with cation A in coordination number 9 and 12. In the case where A = K+ and X = F?, we propose the relationship: where R is the coordination number. 相似文献