共查询到20条相似文献,搜索用时 15 毫秒
1.
Alexander Gribanov Andriy Grytsiv Yurii Seropegin 《Journal of solid state chemistry》2009,182(7):1921-1928
The crystal structures of ternary compounds RPt3−xSi1−y(R=Y, Tb, Dy, Ho, Er, Tm, Yb) have been elucidated from X-ray single crystal CCD data. All compounds are isotypic and crystallize in the tetragonal space group P4/mbm. The general formula RPt3−xSi1−y arises from defects: x≈0.20, y≈0.14. The crystal structure of RPt3−xSi1−y can be considered as a packing of four types of building blocks which derive from the CePt3B-type unit cell by various degrees of distortion and Pt, Si-defects. 相似文献
2.
The new oxyborate phosphors, Na3La9O3(BO3)8:Eu3+ (NLBO:Eu) and Na3La9O3(BO3)8:Tb3+ (NLBO:Tb) were prepared by solid-state reactions. The photoluminescence characteristics under UV excitation were investigated. The dominated emission of Eu3+ corresponding to the electric dipole transition 5D0→7F2 is located at 613 nm and bright green luminescence of NLBO:Tb attributed to the transition 5D4→7F5 is centered at 544 nm. The concentration dependence of the emission intensity showed that the optimum doping concentration of Eu and Tb is 30% and 10%, respectively. 相似文献
3.
Kenny Ståhl Tonci Balic-Zunic K. Michael Eriksen Rasmus Fehrmann 《Journal of solid state chemistry》2005,178(5):1697-1704
The crystal structures of K2S2O7, KNaS2O7 and Na2S2O7 have been solved and/or refined from X-ray synchrotron powder diffraction data and conventional single-crystal data. K2S2O7: From powder diffraction data, monoclinic C2/c, Z=4, a=12.3653(2), b=7.3122(1), , β=93.0792(7)°, RBragg=0.096. KNaS2O7: From powder diffraction data; triclinic , Z=2, a=5.90476(9), b=7.2008(1), , α=101.7074(9), β=90.6960(7), γ=94.2403(9)°, RBragg=0.075. Na2S2O7: From single-crystal data; triclinic , Z=2, a=6.7702(9), b=6.7975(10), , α=116.779(2), β=96.089(3), γ=84.000(3)°, RF=0.033. The disulphate anions are essentially eclipsed. All three structures can be described as dichromate-like, where the alkali cations coordinate oxygens of the isolated disulphate groups in three-dimensional networks. The K-O and Na-O coordinations were determined from electron density topology and coordination geometry. The three structures have a cation-disulphate chain in common. In K2S2O7 and Na2S2O7 the neighbouring chains are antiparallel, while in KNaS2O7 the chains are parallel. The differences between the K2S2O7 and Na2S2O7 structures, with double-, respectively single-sided chain connections and straight, respectively, corrugated structural layers can be understood in terms of the differences in size and coordinating ability of the cations. 相似文献
4.
Liya Zhou Wallace C.H. Choy Jianxin Shi Menglian Gong T.I. Yuk 《Journal of solid state chemistry》2005,178(10):3004-3009
Vacuum ultraviolet (VUV) excitation and photoluminescent (PL) properties of Eu3+ and Tb3+ ion-doped aluminate phosphors, GdCaAl3O7:Eu3+ and GdCaAl3O7:Tb3+ have been investigated. X-ray diffraction (XRD) patterns indicate that the phosphor GdCaAl3O7 forms without impurity phase at 900 °C. Field emission scanning electron microscopy (FE-SEM) images show that the particle size of the phosphor is less than 3 μm. Upon excitation with VUV irradiation, the phosphors show a strong emission at around 619 nm corresponding to the forced electric dipole 5D0→7F2 transition of Eu3+, and at around 545 nm corresponding to the 5D4→7F5 transition of Tb3+. The results reveal that both GdCaAl3O7:RE3+ (RE=Eu, Tb) are potential candidates as red and green phosphors, respectively, for use in plasma display panel (PDP). 相似文献
5.
Zuoliang Liu Guochun Zhang Jianxiu Zhang Peizhen Fu 《Journal of solid state chemistry》2010,183(6):1437-1441
Using Na2CO3-H3BO3-NaF as fluxes, transparent RE:Na3La9O3(BO3)8 (abbr. RE:NLBO, RE=Er, Yb) crystals have been grown by the top seed solution growth (TSSG) method. The X-ray powder diffraction analysis shows that the RE:NLBO crystals have the same structure with NLBO. The element contents were determined by molar to be 0.64% Er3+ in Er:NLBO, 2.70% Yb3+ in Yb:NLBO, respectively. The polarized absorption spectra of RE:NLBO have been measured at room temperature and show that both Er:NLBO and Yb:NLBO have a strong absorption bands near 980 nm with wide FWHM (Full Wave at Half Maximum) (21 nm for Er:NLBO and 25 nm for Yb:NLBO). Fluorescence spectra have been recorded. Yb:NLBO has the emission peaks at 985 nm, 1028 nm and 1079 nm and the emission peak of Er:NLBO is at 1536 nm. Spectral parameters have been calculated by the Judd-Ofelt theory for Er:NLBO and the reciprocity method for Yb:NLBO, respectively. The calculated values show that Er:NLBO is a candidate of 1.55 μm laser crystals and Yb:NLBO is a candidate for self-frequency doubling crystal. 相似文献
6.
Needle-like crystals of V3O7 up to 2 mm in length were grown by a chemical vapor transport method using NH4Cl as a transport agent. The anisotropic magnetic susceptibility was measured for the first time. At 2 K, a spin-flop transition occurs under a magnetic field of 0.1 T. V3O7 is proved to be a uniaxial antiferromagnet with its easy axis parallel to the b-axis of monoclinic structure. A spin structure with antiferromagnetic interaction between layers and ferromagnetic interaction in the layers below the Néel temperature (5.2 K) is suggested. 相似文献
7.
Crystal structure of BaMg2Si2O7 was determined and refined by a combined powder X-ray and neutron Rietveld method (monoclinic, C2/c, no. 15, Z=8, a=7.24553(8) Å, b=12.71376(14) Å, c=13.74813(15) Å, β=90.2107(8)°, V=1266.44(2) Å3; Rp/Rwp=3.38%/4.77%). The structure contains a single crystallographic type of Ba atom coordinated to eight O atoms with C1 (1) site symmetry. Under 325-nm excitation Ba0.98Eu0.02Mg2Si2O7 exhibits an asymmetric emission band around 402 nm. The asymmetric shape of the emission band is likely associated with a small electron-phonon coupling in BaMg2Si2O7. The integrated intensity of the emission band was observed to remain constant over the temperature range 4.2-300 K. 相似文献
8.
Hongwei Yu Shilie Pan Hongping Wu Xiaoyu Dong Zhongxiang Zhou 《Journal of solid state chemistry》2011,184(7):1644-1648
A new ternary borate oxide, K3CdB5O10, has been synthesized by solid-state reaction at 580 °C. The compound crystallizes in the monoclinic space group P21/n with a=7.6707 (7) Å, b=19.1765 (17) Å, c=7.8784 (6) Å, β=115.6083 (49)°, and Z=4. The crystal structure consists of a two-dimensional infinite [CdB5O10] layer, which forms by connecting isolated double ring [B5O10] groups and CdO4 tetrahedra. K atoms filling in the interlayer and intralayer link the layers together and balance charge. The IR spectrum has been studied and confirmed the presence of both BO3 and BO4 groups, and the UV-vis-IR diffuse reflectance spectrum exhibits a band gap of about 3.4 eV. The DSC analysis proves that K3CdB5O10 is a congruent melting compound. 相似文献
9.
K3InF6 is synthesized by a sol-gel route starting from indium and potassium acetates dissolved in isopropanol in the stoichiometry 1:3, with trifluoroacetic acid as fluorinating agent. The crystal structures of the organic precursors were solved by X-ray diffraction methods on single crystals. Three organic compounds were isolated and identified: K2InC10O10H6F9, K3InC12O14H4F18 and K3InC12O12F18. The first one, deficient in potassium in comparison with the initial stoichiometry, is unstable. In its crystal structure, acetate as well as trifluoroacetate anions are coordinated to the indium atom. The two other precursors are obtained, respectively, by quick and slow evaporation of the solution. They correspond to the final organic compounds, which give K3InF6 by decomposition at high temperature. The crystal structure of K3InC12O14H4F18 is characterized by complex anions [In(CF3COO)4(OHx)2](5−2x)− and isolated [CF3COOH2−x](x−1)− molecules with x=2 or 1, surrounded by K+ cations. The crystal structure of K3InC12O12F18 is only constituted by complex anions [In(CF3COO)6]3− and K+ cations. For all these compounds, potassium cations ensure only the electroneutrality of the structure. IR spectra of K2InC10O10H6F9 and K3InC12O12F18 were also performed at room temperature on pulverized crystals. 相似文献
10.
A new borate, LiNaB4O7, has been synthesized and characterized by single-crystal X-ray structure determination. The material crystallizes in the orthorhombic system, noncentrosymmetric space group Fdd2, with unit cell dimensions a=13.325(2), b=14.099(2), c=10.243(2) Å, Z=16, and V=1924.3(7) Å3. Like Li2B4O7, the structure is built of two symmetrically independent, interpenetrating polyanionic frameworks built from condensation of the B4O9 fundamental building block, which is comprised of two distorted BO4 tetrahedra and two BO3 triangles. The interpenetrating frameworks produce distinct tunnels that are selectively occupied by the Li and Na atoms. Large single crystals exhibiting an optical absorption edge with λ<180 nm have been grown via the top-seeded-solution-growth method. The SHG signal (0.15× potassium dihydrogen phosphate (KDP)) is consistent with the calculated components of the SHG tensor and the approximate centrosymmetric disposition of the independent and interpenetrating frameworks. A complete analysis of polarized IR and Raman spectra confirms a close relationship between the title compound and Li2B4O7. 相似文献
11.
Hirofumi Matsuhata Ichiro Nagai Yoshiyuki Yoshida Sigeo Hara Shin-ichi Ikeda 《Journal of solid state chemistry》2004,177(10):3776-3783
We report on the crystallographic structure of the layered perovskite iridate Sr3Ir2O7, investigated using transmission electron microscopy. The space group was found to be Bbcb (, No. 68 in the International Tables for Crystallography) at 315 K. A very fine twin structure with 90° rotation with respect to the c-axis was observed. The crystal structure at temperatures lower than 285 K, where a phase transition from paramagnetism to weak ferromagnetism is known to occur, was also examined. There was no difference in the extinction rule for the diffraction patterns between the two phases. We conclude that there is no change in the space group for this magnetic transition. There still remains the possibility of a change in the rotation angle of IrO6 octahedrons and a corresponding change in the interatomic distance between Ir and O, though. 相似文献
12.
Two novel noncentrosymmetric borates oxides, MBi2B2O7 or MBi2O(BO3)2 (MCa, Sr), have been synthesized by solid-state reactions in air at temperatures in the 600-700 °C range. Their crystal structures have been determined ab initio and refined using powder neutron diffraction data. CaBi2B2O7 crystallizes in the orthorhombic Pna21 space group with a=8.9371(5) Å, b=5.4771(3) Å, c=12.5912(7) Å, Z=4, Rwp=0.118, χ2=2.30. SrBi2B2O7 crystallizes in the hexagonal P63 space group with a=9.1404(4) Å, c=13.0808(6) Å, Z=6, Rwp=0.115, χ2=4.15. Large displacement parameters suggest the presence of disorder in SrBi2B2O7 as also revealed by diffuse 2×a superstructure reflections in electron diffraction patterns. Both structures are built of identical (001) neutral layers of corner-sharing BO3 triangles and MO6 trigonal prisms forming six-membered rings in which Bi2O groups are located. Adjacent layers are stacked in a staggered configuration and connected through weak Bi-O bonds. A moderate efficiency for second harmonic generation (SHG) has been measured for a powder sample of CaBi2B2O7 (deff=2deff(KDP)). 相似文献
13.
Samples in the system Lu2−xYxSi2O7 (0?x?2) have been synthesized following the sol-gel method and calcined to 1300 °C, a temperature at which the β-polymorph is known to be the stable phase for the end-members Lu2Si2O7 and Y2Si2O7. The XRD patterns of all the compositions studied are compatible with the structure of the β-polymorph. Unit cell parameters are calculated as a function of composition from XRD patterns. They show a linear change with increasing Y content, which indicates a solid solubility of β-Y2Si2O7 in β-Lu2Si2O7 at 1300 °C. 29Si MAS NMR spectra of the different members of the system agree with the XRD results, showing a linear decrease of the 29Si chemical shift with increasing Y content. Finally, a correlation reported in the literature to predict 29Si chemical shifts in silicates is applied here to obtain the theoretical variation in 29Si chemical shift values in the system Lu2Si2O7-Y2Si2O7 and the results compare favorably with the values obtained experimentally. 相似文献
14.
Tb3+, Yb3+, Tm3+, Er3+, and Ho3+ doped Ca3(PO4)2 were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb3+-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb3+ content is comparable with that of the commercial Zn2SiO4:Mn2+ green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb3+, Tm3+, Er3+, and Ho3+ doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb3+-Ho3+, Yb3+-Er3+, and Yb3+-Tm3+ in Ca3(PO4)2, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb3+-Tm3+-Er3+-Ho3+ in Ca3(PO4)2, in which the cross-relaxation process between Er3+ and Tm3+, producing the 1D2-3F4 transition of Tm3+, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams. 相似文献
15.
Richard Harrington Gabrielle C. Miles Anthony R. West 《Journal of solid state chemistry》2008,181(2):334-339
Zn7Sb2O12 forms a full range of Co-containing α solid solutions, Zn7−xCoxSb2O12, with an inverse-spinel structure at high temperature. At low temperatures for x<2, the solid solutions transform into the low temperature β-polymorph. For x=0, the β→α transition occurs at 1225±25 °C; the transition temperature decreases with increasing x. At high x and low temperatures, α solid solutions are formed but are non-stoichiometric; the (Zn+Co):Sb ratio is >7:2 and the compensation for the deficiency in Sb is attributed to the partial oxidation of Co2+ to Co3+. From Rietveld refinements using ND data, Co occupies both octahedral and tetrahedral sites at intermediate values of x, but an octahedral preference attributed to crystal field stabilisation, causes the lattice parameter plot to deviate negatively from the Vegard's law. Sub-solidus compatibility relations in the ternary system ZnO-Sb2O5-CoO have been determined at 1100 °C for the compositions containing ?50% Sb2O5. 相似文献
16.
CaIn2O4:Dy3+/Pr3+/Tb3+ blue-white/green/green phosphors were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), diffuse reflectance, photoluminescence (PL) and cathodoluminescence (CL) spectra as well as lifetimes were utilized to characterize the samples. The XRD results reveal that the samples begin to crystallize at 800 °C and pure CaIn2O4 phase can be obtained after annealing at 900 °C. The FE-SEM images indicate that the CaIn2O4:Dy3+, CaIn2O4:Pr3+ and CaIn2O4:Tb3+ samples consist of spherical grains with size around 200-400 nm. Under the excitation of ultraviolet light and low-voltage electron beams (1-5 kV), the CaIn2O4:Dy3+, CaIn2O4:Pr3+ and CaIn2O4:Tb3+ phosphors show the characteristic emissions of Dy3+ (4F9/2-6H15/2 and 4F9/2-6H13/2 transitions, blue-white), Pr3+ (3P0-3H4, 1D2-3H4 and 3P1-3H5 transitions, green) and Tb3+ (5D4-7F6,5,4,3 transitions, green), respectively. All the luminescence is resulted from an efficient energy transfer from the CaIn2O4 host lattice to the doped Dy3+, Pr3+ and Tb3+ ions, and the corresponding luminescence mechanisms have been proposed. 相似文献
17.
Dixie P. Gautreaux John F. DiTusa Julia Y. Chan 《Journal of solid state chemistry》2008,181(8):1977-1982
Five new analogues of the β-CeNiSb3 family have been synthesized and found to be LnNi(Sn,Sb)3 and isostructural to the previously reported β-CeNiSb3. LnNi(Sn,Sb)3 (Ln=Pr, Nd, Sm, Gd, or Tb) crystallizes in the orthorhombic space group, Pbcm, with lattice parameters of a∼12.9 Å, b∼6.1 Å, c∼12.0 Å. The structure consists of layers of nearly square nets of X (X=Sn/Sb) atoms and highly distorted NiX6 octahedra. Lanthanide atoms are located between layers of X and NiX6 octahedra. All analogues are metallic and experimental effective magnetic moments are in agreement with the respective Ln3+ calculated moments. 相似文献
18.
Cr掺杂对K2La2Ti3O10光催化活性的影响 总被引:1,自引:0,他引:1
通过溶胶-凝胶法制备了层状钙钛矿结构的K2La2Ti3O10及Cr掺杂的K2La2Ti3O10,采用X-射线衍射(XRD)、紫外可见漫反射光谱(DRS)、X射线光电子能谱(XPS)等对K2La2Ti3O10及Cr掺杂K2La2Ti3O10进行了表征。以I-为电子给体、分别在紫外和可见光辐射下研究了K2La2Ti3O10及Cr掺杂K2La2Ti3O10光催化分解水的产氢活性。采用第一性原理,计算了Cr掺杂对K2La2Ti3O10半导体能带结构和态密度的影响,从电子结构的变化揭示了掺杂引起光催化活性差异的原因。结果表明,Cr的掺入能够改善和提高K2La2Ti3O10的光解水的产氢活性;Cr改善和提高K2La2Ti3O10的光解水的产氢活性存在一个最佳的掺杂浓度;当Cr与Ti的物质量的比为0.02∶1时,紫外光催化分解水产氢速率为1 500 μmol·L-1·h-1,可见光催化分解水产氢速率为83.6 μmol·L-1·h-1,分别为K2La2Ti3O10掺杂改性前产氢速率的26和5倍。 相似文献
19.
通过调节B2O3‐Bi2O3‐ZnO‐Al2O3(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO3)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明:添加适量的BBZA玻璃能够有效地将BaTiO3陶瓷烧结温度由1350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO3的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO3陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO3晶粒表面。优化的BaTiO3陶瓷制备条件如下:BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO3陶瓷介电常数达到1364,介电损耗低至1.2%。 相似文献
20.
通过调节B2O3-Bi2O3-ZnO-Al2O3(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO3)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明:添加适量的BBZA玻璃能够有效地将BaTiO3陶瓷烧结温度由1 350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO3的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO3陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO3晶粒表面。优化的BaTiO3陶瓷制备条件如下:BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO3陶瓷介电常数达到1 364,介电损耗低至1.2%。 相似文献