4e Sites Research Articles

Order–disorder transition in the (1−x)Li2TiO3–xMgO system (0 ≤ x ≤ 0.5)

The order–disorder phase transition of magnesium lithium titanate solid–solution (1−x)Li2TiO3–xMgO (0 ≤ x ≤ 0.5) ceramics prepared by conventional solid-state processing has been examined. The phase and structural analysis was carried out using electron diffraction, neutron diffraction and high-resolution transmission electron microscopy. Both electron and neutron diffraction results revealed the onset of an order-to-disorder transition at 0.3 < x < 0.4. Superlattice reflections found in certain regions of x = 0.2 samples and most areas of x = 0.3 samples were caused by a twin structure stabilized by Mg incorporation. Rietveld refinements of neutron diffraction data suggested a random distribution of Mg on the Li 4e sites and equal distribution of Mg on the two Ti 4e sites for x ≤ 0.3. As the Mg content continues to increase, the crystal symmetry transforms from monoclinic to cubic rocksalt. Consequently, the cation ordering on the 8f and 4d sites of the C2/c structure became corrupted and turned into short-range ordering on the 4a sites of a cubic structure with symmetry, resulting in diffuse scattering in electron diffraction patterns.

The systems Sr–Zn–{Si,Ge}: Phase equilibria and crystal structure of ternary phases

Phase relations have been established by electron probe microanalysis (EPMA) and X-ray powder diffraction (XPD) for the Sr-poor part of the ternary systems Sr–Zn–Si at 800°C and Sr–Zn–Ge at 700°C. In the Sr–Zn–Si system one new ternary compound SrZn2+xSi2−x (0≤x≤0.45) with CeAl2Ga2 structure and a statistical mixture of Zn/Si in the 4e site was found. Neither a type-I nor a type-IX clathrate phase was encountered. This system is characterized by formation of two further phases, i.e. SrZn1−xSi1+x with ZrBeSi-type (0.16≤x≤0.22) and SrZn1−xSi1+x with AlB2-type (0.35≤x≤0.65) with a random distribution of Zn/Si atoms in the 2c site. For the Sr–Zn–Ge system, the homogeneity regions of the isotypic phases SrZn1−xGe1+x with ZrBeSi-type (0≤x≤0.17) and AlB2-type (0.32≤x≤0.56), respectively, have been determined. Whereas the germanide SrZn2+xGe2−x (CeAl2Ga2-type) is characterized by a homogeneity region (0≤x≤0.5), the clathrate type-I phase Sr8Zn8Ge38 shows a point composition.

Magnetic Properties and Crystal Structure of Melt Spun ${\rm SmCo}_{7-{\rm x}}{\rm Sn}_{\rm x}$ (${\rm x}=0$–0.6) Ribbons

The magnetic properties and crystal structure of melt spun SmCo7-xSnx (x=0-0.6) ribbons have been investigated. The XRD patterns of ribbons spun at a high wheel speed of 40 m/s show that a pure TbCu7-type structure is formed only for x=0.1, while a mixture of CoSn appears at the grain biundary for x ≥ 0.2 and 2:17 phase appears for x ≥ 0.4. The Rietvield refinement result shows that Sn prefers to occupy the 2e sites in TbCu7-type structure, which is similar to Ge. The coercivity of melt spun SmCo7-xSnx ribbons is enhanced from 1.9 kOe for x=0 to 8.4 kOe for x=0.3 . The grain size is reduced with Sn substitution from 100-400 nm for SmCo7 ribbons to 50-100 nm for SmCo6.7Sn0.3 ribbons, which also contributes the coercivity in addition to the enhancement of magnetic anisotropy field by the occupation of Sn atoms at 2e sites.

Crystal structure of τ5–TiNi2−xAl5 (x = 0.48) and isotypic {Zr,Hf}Ni2−xAl5−y

The crystal structure of the compound in the Al-rich region of the Ti–Ni–Al system, τ5–TiNi2−xAl5, x=0.48, has been derived from X-ray powder and single crystal, neutron powder and electron diffraction (space group I4/mmm, a=0.3984(2)nm, c=1.4073(3)nm, RF2=0.0133). Titanium atoms were unambiguously located from neutron powder data. τ5 is isotypic with the crystal structure of ZrNi2Al5. Detailed transmission electron microscopy (TEM) in several crystallographic directions confirmed the lattice parameters and crystal symmetry. Although occupancy of Ni in the 4e site revealed a defect (occ.=0.76), no significant homogeneity region was observed for this phase at 1020°C. Rietveld analyses of X-ray powder diffraction data for the Zr- and Hf-homologues confirmed for both compounds isotypism and revealed defects in the Ni sites and to a lesser extent also in the Al sites: ZrNi2−xAl5−y, x=0.4, y=0.4 and HfNi2−xAl5−y, x=0.5, y=0.2. The crystallographic relations among the structure types of Cu, TiAl3, ZrNi2Al5 and Zr(Ni,Ga)7 have been defined in terms of a Bärnighausen scheme.

Effect of Ge on the magnetic properties and crystal structure of melt spun SmCo7–xGex ribbons

The effect of Ge on the magnetic properties and crystal structure of melt spun SmCo7–xGex (x = 0–0.8) ribbons have been investigated. SmCo7–xGex ribbons (x = 0–0.6) spun at a high wheel speed of 40 m/s crystallize in the TbCu7-type structure. The x-ray diffraction results analyzed by the Rietveld refinement method show that Ge prefers to occupy the 2e sites in the TbCu7-type structure. The grain size of the ribbons is only slightly decreased with the proper amount of Ge substitution (x &amp;lt; 0.7). When increasing x from 0–0.6, the coercivity of the SmCo7–xGex ribbons is enhanced from 1.9 kOe for binary SmCo7 to 7.5 kOe for SmCo6.5Ge0.5 which is mainly due to the enhancement of the magnetic anisotropy field by the Ge substitution for Co in 2e sites. Furthermore, a slight addition of carbon in the alloy is effective in refining the grain size and further improving the coercivity of the ribbons. Coercivity as high as 11.4 kOe could be obtained for SmCo6.7Ge0.3C0.1 ribbons.

Tailoring of structural, electrical and magnetic properties of BaCo2 W-type hexaferrites by doping with Zr–Mn binary mixtures for useful applications

Single-phase W-type hexaferrite, BaCo2Fe16−2x(ZrMn)xO27 (x=0.0–1.0), has been synthesized by the chemical co-precipitation technique. Mössbauer analysis indicates substitution of Zr ions on tetrahedral (4e and 4fIV) sites and Mn ions on the octahedral ‘4fVI site’ at low-doped concentration when the concentration is increased Mn ions but show preference for the octahedral ‘2b site’. The highest enhancement in the value of the room temperature resistivity of 2.82×109Ωcm has been obtained by doping with Zr–Mn content of x=0.6. The dissipation factor increases from 6.49×103 to 9.97×103 at 10kHz with the addition of Zr–Mn dopants. Such materials are potentially suitable for electromagnetic attenuation purposes, for microwave absorption and as radar absorbing material. High values of saturation magnetization (67emu/g) and remanent magnetization (34.7emu/g) are obtained for substitution level of x=0.4 making them suitable for data processing devices.

(Fe, Cr)6Nb6Ox phase of the filled Ti2Ni type with × ± 0.75 in the quaternary Cr–Fe–Nb–O system

Abstract The effect of O on the phase equilibria in Nb–Fe–Cr alloys, more specifically on the formation of a Ti2Ni type phase, has been studied. Nb–xFe–yCr alloys with × = 37.4 – 41.4 at.%, y = 7.6 – 8.6 at.% were subjected to long term annealing experiments at 950 8C after oxygenation. The phases were identified and characterized using scanning electron microscopy, X-ray diffraction and wavelength dispersive spectroscopy. In the pure Nb-37Fe-8Cr and Nb-41Fe-9Cr alloys respectively a two phase equilibrium between (Nb) and l FeNb and a three phase equilibrium between (Nb), l FeNb and Fe2Nb are established. In the oxygenated alloys a Ti2Ni type phase with composition (Fe, Cr)6Nb6Ox appears mainly at the expense of the l FeNb phase. With respect to composition and crystallographic parameters the (Fe, Cr)6Nb6Ox phase has large similarities with the Fe2.4Nb3.6O and Fe6Nb6O phase. From wavelength dispersive spectroscopy measurements, it is concluded that × equals 0.75 when (Fe, Cr)6Nb6Ox is in equilibrium with (Nb), l FeNb and Fe2Nb. × is higher when this phase is in equilibrium with NbO. The structure of (Fe, Cr)6Nb6Ox is also analyzed with Rietveld refinement. This analysis reveals that Cr atoms partially replace Fe atoms only on the 16d site and not on the 32e site.

Structure and electrical properties of the new pyrochlore-type protonic solid electrolyte K0.88Nb2O7.58H4.28

Single-crystal, synchrotron powder X-ray diffraction and neutron powder diffraction studies of the novel pyrochlore-type compound with the structural formula K(0.88)(OH)(0.54)H(1.66)(H(2)O)(1.04)Nb(2)O(6) suggests that the water molecules are located in 32e sites, and the hydroxide ions and potassium ions are located in 16d sites with a significant amount of 'free' protons in 96g sites. The total weight loss at temperatures up to 773 K is only about 8%, suggesting the oxygen escape from 48f sites can be excluded and 'free' protons must be preserved in the structure. The bulk conductivity in ambient air reaches 10(-2) S cm(-1) at 623 K. Owing to the extended stability range and resistance to water solubility, the compound can be considered as a candidate for intermediate temperature solid-oxide fuel-cell applications.

A new class of Sol–gel derived LiM1xM2yMn2−x−yO3.8F0.2 (M1 = Cr, M2 = V; x = y = 0.2) cathodes for lithium batteries

A series of LiM1xM2yMn2−x−yO3.8F0.2 (M1 = Cr, M2 = V; x = y = 0.2) cathodes, viz., LiMn2O3.8F0.2, LiCr0.2Mn1.8O3.8F0.2 and LiCr0.2V0.2Mn1.6O3.8F0.2 along with native LiMn2O4 have been synthesized by Citric Acid assisted Modified (CAM) sol–gel method, with a view to understand the effect of synthesis methodology and the effect of dual category dopants, viz., anion and/or cation upon spinel cathodes individually. An acceptable capacity retention (94%) observed up to 50 cycles for native LiMn2O4 cathodes is attributed to the significance of CAM sol–gel method. Similarly, the encouraging charge–discharge results of LiMn2O3.8F0.2 (130 mAh g−1) and LiCr0.2Mn1.8O3.8F0.2 (142 mAh g−1) cathodes revealed a possible augmentation in the reversible capacity behavior of the spinels upon F− substitution at 32e site and the simultaneous substitution of Cr3+ and F− at 16d and 32e sites respectively.

Crystal structure and physical properties of Yb-based intermetallics Yb(Cu, Ag) 2(Si, Ge) 2, Yb(Cu 1− xZn x) 2Si 2 ( x = 0.65, 0.77) and Yb(Ag 0.18Si 0.82) 2

X-ray powder data for YbCu 2Ge 2, YbAg 2Si 2 and YbAg 2Ge 2 confirmed the atom order of the ThCr 2Si 2 type (ordered BaAl 4 type) as reported earlier. YbCu 2Ge 2 is an intermediate valence system with the Yb ions valence close to +2 at low temperatures, whereas the other two compounds are weakly temperature-dependent paramagnets. All these ternaries show metallic character of their electrical conductivity. The structure of Yb(Cu 1− x Zn x ) 2Si 2 ( x = 0.65, 0.77) was found to correspond to the BaAl 4 type, assuming a random distribution of Cu and Zn atoms over the positions 4d (0, 1/2, 1/4). The Si atoms were found in the sites 4e (0, 0, z). These two pseudoternary compounds are diamagnetic. A novel phase with the composition Yb(Ag 0.18Si 0.82) 2 crystallizes in the ThSi 2-type on the verge to a symmetry reduction towards orthorhombic GdSi 2-type. This phase is a Pauli paramagnet and exhibits metallic behavior of the resistivity.

Crystal structure and magnetic properties of melt spun SmCo7−xMx (M=Ta, Cr, and Mo; x=–0.6) ribbons

The crystal structure and magnetic properties of melt spun SmCo7−xMx (M=Ta, Cr, and Mo; x=0–0.6) ribbons have been investigated. Based on x-ray diffraction analysis, it is found that a pure TbCu7-type structure is formed in the melt spun SmCo7−xTax (x=0–0.3) ribbons, while minor amount of additional 2:17 phase appears for the SmCo7−xMx (M=Cr and Mo; x=0.1–0.6) ribbons, implying that the elements in VIB group (Cr and Mo) are inferior to the element in VB group (Ta) in stabilizing metastable 1:7 phase. The result, analyzed by Rietveld refinement method, shows that Ta, Cr, and Mo may occupy the 2e site of 1:7 phase, which leads to the enhancement of the magnetic anisotropy field of 1:7 phase, just like Ti, Zr, Hf, Nb, or V did. From the magnetic performance point of view, with increasing the content of doping element x from 0 to 0.6, the maximum coercivity of SmCo7−xMx ribbons is enhanced from 1.9 kOe for binary SmCo7 to 11.3 kOe for M=Ta, 6.6 kOe for M=Cr, and 7.5 kOe for M=Mo, respectively, while the remanent magnetization is all reduced for the above ternary alloy ribbons.

Zn3(PO4)2(H2O)0.8(NH3)1.2

The structure of the title compound, ammineaquadi-mu(5)-phosphato-trizinc(II), [Zn(3)(PO(4))(2)(H(2)O)(0.8)(NH(3))(1.2)], consists of two parts: (i) PO(4) and ZnO(4) vertex-sharing tetrahedra arranged in layers parallel to (100) and (ii) ZnO(2)(N/O)(2) tetrahedra located between the layers. Elemental analysis establishes the ammine-to-water ratio as 3:2. ZnO(2)(N/O)(2) tetrahedra are located at special position 4e (site symmetry 2) in C2/c. The two O atoms of ZnO(2)(N/O)(2) are bonded to neighbouring P atoms, forming two Zn-O-P linkages and connecting ZnO(2)(N/O)(2) tetrahedra with two adjacent bc plane layers. A noteworthy feature of the structure is the presence of NH(3) and H(2)O at the same crystallographic position and, consequently, qualitative changes in the pattern of hydrogen bonding and weaker N/O-H...O electrostatic interactions, as compared to two closely related structures.

Enhancement of coercivity for melt-spun SmCo7−xTax ribbons with Ta addition

The effect of Ta addition on the structure and magnetic properties of melt-spun SmCo7−xTax (x=0–0.6) ribbons has been investigated. The intrinsic coercivity increases dramatically from 1.9 kOe for Ta-free ribbon to 9.8 kOe for SmCo6.7Ta0.3 ribbon, while further increasing Ta results in little enhancement of the coercivity. XRD patterns reveal that SmCo7−xTax ribbons crystallize in the pure TbCu7-type structure for low Ta substitution of x≤0.3 and a minor phase of TaCo3 appears when x&amp;gt;0.3. According to Rietveld structure refinement, the ternary alloying element Ta prefers to occupy the 2e site of TbCu7-type structure. The mechanism of the coercivity enhancement has been discussed based on crystal structure and microstructure.

Crystal Structure, Diffusion Path, and Oxygen Permeability of a Pr2NiO4-Based Mixed Conductor (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+δ

We have investigated in situ the crystal structure, oxygen diffusion path, oxygen permeation rate, and electrical conductivity of a doped praseodymium nickel oxide, Pr(2)NiO(4)-based mixed conductor, (Pr(0.9)La(0.1))(2)(Ni(0.74)Cu(0.21)Ga(0.05))O(4+delta) (PLNCG) in air between 27 degrees C and 1015.6 degrees C. The PLNCG has a tetragonal I4/mmm K(2)NiF(4)-type structure which consists of a (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) perovskite unit and a (Pr(0.9)La(0.1))O rock salt unit in the whole temperature range. Both experimental and theoretical electron density maps indicated two-dimensional networks of (Ni(0.74)Cu(0.21)Ga(0.05))-O covalent bonds in PLNCG. Highest occupied molecular orbitals (HOMO) in PLNCG demonstrate that the electron-hole conduction occurs via Ni and Cu atoms in the (Ni(0.74)Cu(0.21)Ga(0.05))-O layer. The bulk oxygen permeation rate was high (137 mumol cm(-2) min(-1) at 1000 degrees C), and its activation energy was low (51 kJ mol(-1) at 950 degrees C). The Rietveld method, maximum-entropy method (MEM), and MEM-based pattern fitting analyses of neutron and synchrotron diffraction data indicate a large anisotropic thermal motion of the apical O2 oxygen at the 4e site (0, 0, z; z approximately 0.2) in the (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) perovskite unit. Neutron and synchrotron diffraction data and theoretical structural optimization show the interstitial oxygen (O3) atom at (x, 0, z) (x approximately 0.6 and z approximately 0.2). The nuclear density analysis indicates that the bulk oxide-ion diffusion, which is responsible for the high oxygen permeation rate, occurs through the interstitial O3 and anisotropic apical O2 sites. The nuclear density at the bottleneck on the oxygen diffusion path increases with temperature and with the oxygen permeation rate. The activation energy from the nuclear density at the bottleneck decreases with temperature, which is consistent with the decrease of the activation energy from oxygen permeation rate. The extremely low activation energy (12 kJ mol(-1) at 900 degrees C) from the nuclear density at the bottleneck indicates possible higher bulk oxygen permeation rates in quality single crystals and epitaxial thin films.

Effects of Substitution in Barium Hexaferrites BaFe12-xXxO19 (X=Co,Ti; Sc)

The short and long-range atomic and magnetic order in BaFe12-xCoxTixO19 (x=0.4, 0.7, 0.8) and BaFe10.4Sc1.6O19 prepared by soft chemistry routes were studied and compared with parent BaFe12O19 prepared by solid-state reaction. For BaFe10.3Co0.85Ti0.85O19 neutron diffraction and magnetic measurements revealed that (Co2+, Ti4+) substitution causes significant distortions in the local oxygen surrounding of ferric cation sites, while the grain-size effect on the structural parameters is considerably smaller. The thermal expansion coefficient exhibits a strong anisotropy. The refined magnetic moments for x=0.45 and 0.7 based on the five-cation sublattice block-type collinear ferrimagnetic structure of uniaxial type known as Gorter type for BaFe12O19, are considerably lower than the theoretical spin only moments, especially for the 4e and 12k sites, indicating for x = 0.7 a local noncollinearity with short-range ordering. For x = 0.85, at 10 K a block-type conical magnetic structure sets in. For BaFe10.4Sc1.6O19, combined neutron diffraction, field-dependent 57Fe Mössbauer studies and magnetic measurements show that the collinear block-type structure remains effective at 300 K and below it down to about 190 K. In the 190 – 1.6 K range we observe a temperature dependent incommensurate complex block-type conical structure.

MAGNETIC PROPERTIES AND CRYSTAL STRUCTURE OF MELT SPUN Sm(Co, M)7 RIBBONS (M = Hf, V, Nb, andTa)

Magnetic properties and crystal structure of melt spun SmCo 7-x M x ( M = Hf , V , Nb , and Ta ; x = 0–0.3) ribbons have been investigated. The experimental results showed that not just Hf but also V , Nb and Ta prefer to occupy 2e site in the TbCu 7 structure and remarkably increase coercivity of the ribbons from 1.7 kOe for x = 0 to 10–12 kOe for x = 0.2, which would be due to the increase of magnetic anisotropy field by the element substitution. Furthermore, the effect of C addition on the magnetic properties and microstructure of melt spun Sm ( Co , M )7 ribbons were also studied. A small amount of C addition in the ribbons could effectively refine their microstructure, and leads to further improvement of the magnetic properties. The optimal magnetic properties of B r = 6.9 kG , i H c = 11.8 kOe and ( BH ) max = 10.6 MGOe were attained for SmCo 6.8 Hf 0.2 C 0.12 nanocomposites.

Characterization of copper sulfide nanostructured spheres and nanotubes synthesized by microwave-assisted solvothermal method

Copper sulfide nanostructured spheres and nanotubes were successfully synthesized, using a microwave-assisted solvothermal method, by the decomposition of [Cu(CH 3CSNH 2) 2]Cl 2 complexes, formed by the reaction of CuCl 2·2H 2O and CH 3CSNH 2 in ethylene glycol at different pH values, and identified by CHNS/O and FTIR analyses. The decrease in bonding energy of N–H revealed the coordination of copper ions and thioacetamide molecules. It was specified that nitrogen atoms of thioacetamide molecules were used to form Cu–thioacetamide complexes. XRD, SEM, TEM and SAED analyses show that the products were hexagonal CuS spheres in an extremely low pH solution, and hexagonal CuS nanotubes at a pH 13. Their Raman spectra show sharp peaks at 473 cm − 1 , identified as the S–S stretching mode of S 2 ions at the 4e sites.

Electronic structures and magnetic properties in SmCo7–xMx

The electronic structures and magnetic properties of SmCo7-xMx (M = Ti, Si, Zr, Hf, Cu, B, Ag, Ga, Mn) compounds are investigated by using a spin-polarized MS-X.α method. The results show that the long-range ferromagnetic order is determined by a stronger 3d_5d interaction, rather than the traditional RKKY interaction, and the effects of doping element M on 3d_5d coupling are negligible in Sm-Co-based compounds. The nonmagnetic dopant Si atoms have a larger effect on the moments of 2e site although they preferably occupy the Co 3g sites, which results in the stronger uniaxial anisotropy of this compound. Analysis of the formation energies indicates that 5d-element doped compounds are more stable than other dopants, and furthermore, they have a higher Curie temperature above room temperature, which will be in favor of their potential application as high-temperature permanent magnets.

Die Selten-Erd-Metall(III)-Fluorid-Oxoselenate(IV) MF[SeO3] (M = Y, Ho–Lu) imYF[SeO3]-Typ/ The Rare-Earth Metal(III) Fluoride Oxoselenates(IV) MF[SeO3] (M = Y, Ho–Lu) with YF[SeO3]-type Structure

YF[SeO3]-type rare-earth metal(III) fluoride oxoselenates(IV) MF[SeO3] (M = Y, Ho-Lu) crystallize monoclinically in space group P21/c (no. 14) with Z = 4. Obeying the lanthanoid contraction, the lattice parameters decrease successively from a = 657.65(7), b = 689.71(7), c = 717.28(7) pm and β = 99.036(5)° for YF[SeO3] at 298 K to a = 648.39(6), b = 681.28(7), c = 705.81(7) pm and β = 98.657(5)° for LuF[SeO3] at 100 K (LT-LuF[SeO3], LT ≡ Low Temperature). The M3+ cations are occupying the general site 4e. Contrary to the triclinic structure of RT-LuF[SeO3] (RT ≡ Room Temperature; CN(Lu3+) = 7) the higher coordination number eight is achieved for the M3+ cations in all YF[SeO3]-type compounds. This results in [MO6F2]11− polyhedra (d(M-O) = 228 - 243/225 - 239 plus 263/258 pm, d(M-F) = 219/216 pm, M = Y/Lu), which are connected via common O・ ・ ・O edges to form infinite chains 1 ∞{[MOe 4/2Ot 2/1Ft 2/1]7−} (e ≡ edge-sharing, t ≡ terminal) running along [010]. Neighboring chains share common O3・ ・ ・O3 and O3・ ・ ・F edges generating 2 ∞{[M(O3)3/3(O2)2/2(O1)1/1F2/2]4−} sheets parallel to the (100) plane. Finally, these 2 ∞{[MO3F]4−} sheets are interconnected by Se4+ cations, which appear in isolated ψ1-tetrahedral [SeO3]2− anions (d(Se-O) = 167 - 175 pm). For the synthesis of the YF[SeO3]-type rare-earth metal(III) fluoride oxoselenates( IV) MF[SeO3] (M = Y, Ho-Lu), the rare-earth metal sesquioxides (M2O3) and trifluorides (MF3), and selenium dioxide (SeO2) in molar ratios of 1 : 1 : 3 with the fluxing agent CsBr were reacted within five days at 700 - 750 °C in evacuated graphitized silica ampoules.

Magnetic properties, phase evolution, and structure of melt spun SmCo7−xNbx (x=0–0.6) ribbons

The phase evolution, microstructure, and magnetic properties of melt spun SmCo7−xNbx (x=0–0.6) ribbons have been investigated using powder x-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer, respectively. SmCo7−xNbx ribbons could crystallize in TbCu7-type structure only for low Nb substitution of x=0–0.3 at high wheel speed of 30–40 m/s. According to the structure refinement, the doping element Nb prefers to occupy the 2e site. The intrinsic coercivity increases dramatically from 1.9 kOe for SmCo7 ribbon to 10.2 kOe for SmCo6.8Nb0.2 ribbon at wheel speed of 40 m/s. The mechanism of the coercivity enhancement has been discussed. The optimal magnetic properties of σr=54.4 emu/g and Hic=10.2 kOe were obtained in SmCo6.8Nb0.2 ribbon.