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1.
A series of isotypic silicates of composition RE2M[SiO4]2 (OH) with RE = La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, and M = Al3+, Fe3+ has been synthesized under hydrothermal conditions. Lattice constants of two members as determined from single crystal X-ray diffraction data are: La2Al[SiO4]2 (OH) (La2Fe[SiO4]2 (OH)) , , , gb = 112.4 (112.5°), , Z=4. 相似文献
2.
P.B. Fabritchnyi A.N. Protsky V.P. Gorkov G. Demazeau P. Hagenmuller 《Materials Research Bulletin》1981,16(4):429-435
Hyperfine magnetic interactions have been observed for the first time for Sn2+ ions introduced as doping agents in a magnetically ordered oxide (119Sn: Cr2O3). Mössbauer resonance at low temperature shows for 119Sn2+ the simultaneous presence of hyperfine magnetic and quadrupole interactions, which have the same order of magnitude at 77 K. From the spectra, the following parameters have been determined: tranfered hyperfine magnetic field: HSn2+ (77 K = 38 ± 1kOe, sign and value of the quadrupole interaction constant: eVzzQ = + 3,6 ± 0,3 mm/s, asymmetry parameter: η = 0,15 ± 0,05, polar (θ) and azimutal (?) angles: , and chemical shift: . The investigation shows that Sn2+ is localized at the surface of the Cr2O3 grains. 相似文献
3.
The crystal structure of 6H-RbMgF3 has been more precisely determined by using the crystal data of isostructural RbNiF3. It crystallizes in the hexagonal P63/mmc space group with the parameters: and .Both magnesium positions can be occupied by Ni2+ and detected by ESR. Analysis of the spectra reveals one site (octahedra sharing one face) corresponding to an important zero field splitting (D = 2,37 cm?1) and another one of higher symmetry corresponding to the corner-sharing octahedra. 相似文献
4.
Panli You Guangfu Yin Xianchun ChenBo Yue Zhongbing HuangXiaoming Liao Yadong Yao 《Optical Materials》2011,33(11):1808-1812
A series of single-phase full color phosphors, Dy3+-doped Li2SrSiO4 was synthesized by a solid-state reaction method. The phase of the as-prepared powders was measured by X-ray diffraction pattern (XRD) and the chemical composition was characterized using energy dispersive spectroscopy (EDS). The luminescent properties of Li2SrSiO4:Dy3+ were systematically investigated by concentration quenching, decay behavior and thermal stability measurements. The results suggested that the emission intensity of the Li2SrSiO4:Dy3+ was much stronger than that of Li2SrSiO4:Eu2+. It was worth to mention that Li2SrSiO4:Dy3+ phosphor possessed excellent thermal stability for use in light-emitting diodes (LEDs) and the emission intensity measured at 300 °C was only decreased 8% comparing with that measured at room temperature. Furthermore, the Commission International del’Eclairage (CIE) chromaticity coordinates of Li2SrSiO4:Dy3+ moved toward the ideal white light coordinates (0.33, 0.33). All results demonstrated that Li2SrSiO4:Dy3+ might be a potential phosphor for NUV-based white light-emitting diodes. 相似文献
5.
The system PbS-In2S3 was examined by differential thermal analysis (DTA), chemical vapour transport (CVT), and X-ray diffraction. Five new phases of compositions closely related to the 1:1 ratio were found and prepared as needle-shaped single-crystals; their crystal data are reported. The structures of PbIn2S4 (orthorhombic, Pnma, a=11.688(1), b=3.8528(1), , Z=4) and Pb6In10S21 (monoclinic, C2/m, a=27.629(3), b=3.8630(5), , β=95.9°, Z=2 were solved from 808 resp. 3554 independent reflexions and refined to R=0.116 resp. 0.068. In both structures the In-S coordination polyhedra are distorted octahedra, the Pb-S polyhedra are distorted bicapped trigonal prisms. 相似文献
6.
Four intermediate phases are present ; PbGa2S4,orthorombic EuGa2S4-type (a = 20,44 ; b = 20,64 ; ) ; Pb2Ga2S5, orthorombic space group Pbca (a = 12,38 ; b = 11,90 ; ) ; and two Ga2S3-rich solid solutions, one of the wurtzite type at temperatures above 1000°C, one of the distorded blende type below about 970°C. PbGa2S4 has a peritectic decomposition at 930°C, and Pb2Ga2S5 at 900 ± 5°C. The eutectic is at 730°C for about n = 0,80 ( atomic). A glassy region is obtained by quenching the liquid phase and its extent depends on the quenching temperature (at 1000°C, between n = 0,25 and n = 0,50). 相似文献
7.
The preparation and luminescence properties of manganese activated strontium borate have been studied. Divalent manganese emits green light at 512 nm in the SrB6O10 matrix. The emission is weak when excited with UV-radiation but can be improved with sensitizers, Pb2+ and Sn2+, having emission in the UV (312 nm) and blue regions (430 nm), respectively. Divalent lead proved to be a better sensitizer than tin and greatest emission brightness was obtained with a Mn2+ concentration of 4 % and Pb2+ concentration of about 15 %. Complete energy transfer from sensitizer to activator was not obtained with either Pb2+ or Sn2+.The emission wavelength of (Sr0.8Mn0.04Pb0.16)B6O10 at 512 nm is somewhat too short for a low-pressure fluorescence lamp containing three phosphors. The wavelength can be slightly lengthened by the addition of Ba, Ca or Cd, but there is then a dramatic decrease in the emission intensity of manganese. 相似文献
8.
Single crystals of orthorhombic Pb3O2I2 could be prepared by annealing a mixture of 2PbO + PbI2 at 400 °C. Cell parameters are a = 17.862(3), b = 5.954(1), and ; space group is Pnma. The structure was determined from 1121 independent reflections and refined to R = 3.16%. It is built up by edge-shared Pb4O tetrahedra, forming Pb6O4 double chains parallel to [010], which are connected by iodine. Three anion coordinations of lead can be distinguished: Pb(1) forms a bicapped triangular prism with 4 oxygen and 4 iodine atoms (4+4), Pb(3) a monocapped prism (2+5), whereas Pb(2) is octahedrally (2+4) surrounded; all coordination polyhedra are distorted. Structural relationships to Pb3O2Cl2 exist. 相似文献
9.
Roger Salmon Claude Parent Marcus Vlasse Gilles Le Flem 《Materials Research Bulletin》1979,14(1):85-89
A new sodium ytterbium orthophosphate with general formula Na3(1+x)Yb(2-x)(PO4)3 (0.07 ? x ? 0.50) has been prepared and characterized. Its crystal structure has been determined from a single crystal for x = 0.50. The space group is R3?c, the lattice constants are : , . The structure of Na4.50Yb1.50(PO4)3 is related to that of NaZr2(PO4)3. The PO4 tetrahedra and the (Yb,Na)O6 octahedra form a three-dimensional skeleton in which the remaining sodium atoms are inserted. This structural type is also found for the phases Na4.50Ln1.50(PO4)3 (Ln = Tm, Lu) and Na4.50Ln1.50(AsO4)3 (Ln = Er, Tm, Yb, Lu). 相似文献
10.
The temperature dependence of the critical stress in ferroelastic Pb3 (PO4)2 reveals a Curie-Weiß law () up to 145°C. Between 160°C and the transition point at 180°C a crossover to a regime was found. For mixed crystals Pb3 (PO4)2 ? Pb3 (VO4)2 a phase diagram is suggested from optical, dielectric and Raman spectroscopical experiments. 相似文献
11.
Pb3ZrF10 crystallizes with orthorhombic symmetry, space group : Cmcm and unit-cell parameters : , , (Z = 4). Its structure has been solved and refined to a conventional R = 0,041 for 350 independent reflexions. It can be described as an ordered intergrowth of (Pb2F4)n fluorite like monodimensional units and (Pb4Zr2F16)n columnar clusters built of two isolated square antiprisms sharing faces with four [PbF11] complex polyhedra.A structural mechanism based on the transformation of edgesharing fluorite cubes to isolated square antiprisms is proposed to explain the change from fluorite to the anion-excess fluorite like Pb3ZrF10 structure.Analogies with homologous structures are discussed. 相似文献
12.
Pb3ZrF10 crystallizes with orthorhombic symmetry, space group : Cmcm and unit-cell parameters : , , (Z = 4). Its structure has been solved and refined to a conventional R = 0,041 for 350 independent reflexions. It can be described as an ordered intergrowth of (Pb2F4)n fluorite like monodimensional units and (Pb4Zr2F16)n columnar clusters built of two isolated square antiprisms sharing faces with four [PbF11] complex polyhedra.A structural mechanism based on the transformation of edgesharing fluorite cubes to isolated square antiprisms is proposed to explain the change from fluorite to the anion-excess fluorite like Pb3ZrF10 structure.Analogies with homologous structures are discussed. 相似文献
13.
The cell parameters of the ferroelastic and ferroelectric phase of Pb3V2O8 (T < 262 K) have been determined by very accurate X-ray powder diffractometry ; at 77 K, , , and . This monoclinic cell is characterized by Z = 2 and the space group is A2. Thermal expansion tensors have been measured versus temperature for the three phases α (T < 262K), β (262K < T < 360 K) and γ (T > 360 K). The intermediate phase β is characterized by an important thermal expansion anisotropy and its molecular volume is higher than that of the two other phases α and γ. 相似文献
14.
R. Jabłoński 《Materials Research Bulletin》1973,8(8):909-914
Superhyperfine structure s.h.f.s. resulting from the Cr2+ - F? interaction was studied in Cr2+ doped CdF2 crystals. The s.h.f.s. observed can be described with by the following spin-Hamiltonian The constants calculated are . The measurements were made with an ESR spectrometer at X band at 4.2 OK. 相似文献
15.
Samples in the system PbOPbF2Nb2O5NbO2F prepared at 875 K and 1025 K were studied by X-ray single crystal and powder diffraction as well as electron diffraction methods. Six new compounds were characterized as Pb0.74Nb10.62(O,F)30 (orth.), Pb1.36Nb10.91(O,F)30 (tetr.), Pb0.27Nb(O,F.)3.17 (hex.), Pb2Nb3O7F5 (tetr.), Pb0.75NbO3F0.5 (tetr.) and Pb1?Nb(O,F)2+ (cub.) 相似文献
16.
M. Meyer G. Venturini B. Malaman J. Steinmetz B. Roques 《Materials Research Bulletin》1983,18(12):1529-1535
LuMnGe2 has been studied by single - crystal X-ray diffraction analysis. The structure is of a new type with space group Cmmm and Z = 12: a = 5.466(2), b = 18.519(7), , Dx = 9.03 Mg m?3, μ(AgKα) = 31 mm?1, F(000) = 1919, R = 0.030 for 593 independant reflexions (Rw = 0.034). The LuMnGe2 structure type had been predicted and completes a large structural family TT′Si(Ge)2 where T = Nb, Ti, Zr, Hf, Sc, Lu and T′ = Cr, Mn, Re, Fe, Co, where ScMnGe2 is another new member, isostructural with TiMn(Fe)Si2 相似文献
17.
C.S. Sunandana 《Materials Research Bulletin》1985,20(5):531-537
An ESR study of the ‘products’ of the high temperature solid state reaction xCr2O3+yV2O5 (), aided by powder X-ray diffraction and IR spectra, has revealed (i) ‘unfamiliar’ paramagnetic intermediates Cr4+ and Cr5+, (ii) provided some clues to the oxidation of Cr3+ to Cr6+, and (iii) demonstrated a variety of exchange interactions involving V4+ and Cr3+. 相似文献
18.
Wangdong Liu Hanchao Wang Shiping Zhan Wenbin Li 《Journal of Materials Science》2011,46(23):7620-7625
Although Eu3+ ion-doped Y2O3 has been extensively used as red phosphors, their color rendering needs to be improved for high-quality illumination and
displaying. Here, we show that the emission spectra of Y2O3:Eu3+ red phosphors can be broadened by the doping of Nd3+ ion so that the color rendering capability of Y2O3:Eu3+ was remarkably enhanced. Y2O3:Eu3+ and Y2O3:Eu3+,Nd3+ colloidal spheres were synthesized by wet chemical procedure and high-temperature treatment. The fluorescence measurement
under the 254 and 380 nm ultraviolet excitation indicates that the 612 nm red emission peak of Eu3+ can be splitted into two ones by the doping of Nd3+ ion, of which the full width at half maximum (FWHM) is broadened from 4.2 nm to 9.6 nm. By varying the concentration of Nd3+ ion, it was determined that the optimal doping concentration of Nd3+ ion is of 3 mol% for realizing the strongest emission intensity. The further increase of Nd3+ ion exceeding 3 mol% would lead to a concentration quenching phenomenon. The analysis based on XRD spectra and the simplified
energy diagram suggested that the doped Nd3+ ion not only monitored the growth dynamics, but also took an efficient energy transfer and a cross relaxation process to
generate intense emission from Eu3+ ion in both of C2 and S6 sites, instead of preferable one type of Eu3+ site (C2 or S6) in the Nd3+ undoped sample. 相似文献
19.
Anders G. Nord 《Materials Research Bulletin》1983,18(5):569-579
A number of solid solutions of 3(PO4)2 in Cd3(PO4)2 have been prepared and equilibrated at 1070 K (). The respective ( phases are either isotypic with β′-Cd3(PO4)2 or with the mineral graftonite, both with five- and six- (or even seven)-coordinated cations. The monoclinic unit cell dimensions have been accurately determined from Guinier-Hägg photographs, and complete X-ray powder diffraction data are given for β′-Cd3(PO4)2. The cell volumes are strongly correlated to the size and amount of incorporated 2+ cation. The homogeneity regions and structures of the (Cd,)3(PO4)2 phases, though, seem rather to be controlled by the cation ordering. 相似文献
20.
An ordered ramsdellite Li3FeSb2O8, called triramsdellite, was synthesized for the first time. This phase crystallizes in the orthorhombic system, with the possible space groups Pmcn and P21 cn and with the parameters , and . The X-ray powder diffraction study shows that a 1–2 type order appears between the cations belonging to the two sorts of octahedral sites A and B; these sites are preferentially occupied by lithium and antimony respectively according to the formulation |Li3|tet|Li1.5Fe0.5|Aoct|FeSb3|BoctO12. This structure, which can be described as built up from A2B4O12 octahedral units, is compared to the LiSbO3 and trirutile structures. 相似文献