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1.
Ternary R3Pd4Ge4 samples (R=Nd, Eu, Er) were investigated by means of X-ray single crystal (four circle diffractometer Philips PW1100, MoK radiation) and powder diffraction (MX Labo diffractometer, CuK radiation). The Er3Pd3.68(1)Ge4 compound belongs to the Gd3Cu4Ge4 structure type, space group Immm, a=4.220(2) Å, b=6.843(2) Å, c=14.078(3) Å, R1=0.0484 for 598 reflections with Fo>4σ(Fo) from X-ray single crystal diffraction data. No ternary R3Pd4Ge4 compound when R is Nd or Eu was observed. The Nd and Eu containing samples appeared to be multiphase. Ternary phases observed in the Nd3Pd4Ge4 and Eu3Pd4Ge4 alloys and their crystallographic characteristics are the following: NdPd2Ge2, CeGa2Al2 structure type, space group I4/mmm, a=4.3010(2) Å, c=10.0633(2) Å (X-ray powder diffraction data); NdPd0.6Ge1.4, AlB2 structure type, space group P6/mmm, a=4.2305(2) Å, c=4.1723(2) Å (X-ray powder diffraction data); Nd(Pd0.464(1)Ge0.536(1))2, KHg2 structure type, space group Imma, a=4.469(2) Å, b=7.214(2) Å, c=7.651(3) Å, R1=0.0402 for 189 reflections with Fo>4σ(Fo) (X-ray single crystal diffraction data); Eu(Pd,Ge)2, AlB2 structure type, space group P6/mmm, a=4.311(2) Å, c=4.235(2) Å; EuPdGe, EuNiGe structure type, space group P21/c, and ternary compound with unknown structure (X-ray powder diffraction data). 相似文献
2.
G. V. Ivanova G. M. Makarova Ye. V. Shcherbakova Ye. V. Belozerov A. S. Yermolenko 《Journal of Alloys and Compounds》1997,260(1-2):139-142
The phase content of the Sm(Fe1−xSix)y alloys (0.05≤x≤0.15; 8.5≤y≤12) has been studied by X-ray diffraction using micromonocrystals. The compounds Sm2(Fe,Si)17, Sm(Fe,Si)12 and a novel Sm3(Fe,Si)29 compound with a monoclinic unit cell are found. The lattice parameters of Sm3(Fe,Si)29 are: a=1.056 nm, b=0.850 nm, c=0.966 nm, β=96.8°. This compound forms as a result of a solid state transformation from the high-temperature Sm2(Fe,Si)17 phase. Diffuse effects observed in rocking photographs suggest transition structures arising from this transformation. The Curie temperatures of Sm3(Fe,Si)29 vary in the interval 496–521 K. 相似文献
3.
P. Salamakha A. P. Gonalves O. L. Sologub M. Almeida 《Journal of Alloys and Compounds》2003,360(1-2):61-68
The crystal structure of the ternary boride Y2Pd14B5, space group I41/amd, a=8.484(2) Å, c=16.490(3) Å, V=1186.98 Å3, Z=4, was refined down to R=0.0475, wR2=0.1276 from single crystal X-ray diffraction data. Two types of coordination for boron atoms were observed: the coordination sphere for the B1 atom is a trigonal prism with one additional atom; the B2 atom has only four neighboring atoms which form a square. No boron–boron contact was observed. Analysis of the Y2Pd14B5 crystal structure shows the existence of a correlation between this structure and the Sc4Ni29B10 structure type. Magnetization and AC susceptibility measurements indicate that there is no superconducting or magnetic transition in Y2Pd14B5 down to 2 K. 相似文献
4.
《Journal of Alloys and Compounds》1997,260(1-2):157-161
The crystal structures of three new ternary silicides Sc3Pr2Si4, Sc1.26Pr3.74Si4 and Sc3.96Nd1.04Si4 were determined by single crystal X-ray diffraction. The title compounds crystallize with three different substitution derivatives of the Sm5Ge4 structure type (orthorhombic space group Pnma) containing various distributions of rare earth atoms on the three Sm sites. Crystal chemistry analysis shows that these distributions are controlled by the atomic size factor. 相似文献
5.
A.V. Kolomiets S. MaškováL. Havela Z. Mat?jR. Ku?el 《Journal of Alloys and Compounds》2011,509(10):4185-4189
The paper is focusing on the modification of the crystal lattice upon the hydrogenation of La2Pd2In and hydrogen desorption from La2Pd2In hydrides. The synthesis at 1 bar of hydrogen produces a crystalline hydride with 1.5 H atoms per formula unit and the volume expansion of ΔV/V = 6.0%. The synthesis at 10 and 100 bar H2 pressures leads to an amorphous state and with 4 + δ H atoms/f.u. The uptake of hydrogen leads to the decrease of the Debye temperature of La2Pd2In and modification of the optical phonon spectrum. 相似文献
6.
X.Z. Li X.L. Chen L. Wu Y.G. Cao T. Zhou Y.P. Xu 《Journal of Alloys and Compounds》2004,370(1-2):53-58
A new modification of the compound Ba3YB3O9, β phase, has been attained through solid phase transition from phase at 1125–1134 °C. β-Ba3YB3O9 crystallizes in the hexagonal space group
with cell parameters a=13.0529(8) Å, c=9.5359(9) Å. The crystal structure of -Ba3YB3O9 has been determined from powder X-ray diffraction (XRD) data. The refinement was carried out using the Rietveld methods and the final refinement converged with Rp=8.8%, and Rwp=11.8% with Rexp=5.65%. In its structure, the isolated [BO3]3− anionic groups are parallel to each other and distributed layer upon layer along the c-axis. The Y atoms are six-coordinated by the O atoms to form octahedra. The result of IR spectrum confirmed the existence of [BO3]3− triangular groups. 相似文献
7.
P. Salamakha O. Sologub A. P. Gonalves M. Almeida 《Journal of Alloys and Compounds》2003,360(1-2):131-136
The crystal structure of a new ternary boride Ce2Ir5B2, space group
, a=5.477(2) Å, c=31.518(5) Å, Z=6, V=818.79 Å, was refined down to R=0.0484, wR2=0.1211 from single crystal X-ray diffraction data. This is the first representative of a new structure type of intermetallic compounds (an ordered variant of the binary Er2Co7 compound). The structure of Ce2Ir5B2 is the stacking variant of the MgCu2- and CeCo3B2-type slabs and belongs to the structural series with the general formula R2+nM4+3nX2n (n=2). 相似文献
8.
A new compound with chemical formula YbZn2As2 and ‘anti’-La2O3-type crystal structure (space group P3m1) has been synthesized for the first time. The trigonal lattice constants of the compound are a=0.4157 and c=0.6954 nm. In the temperature range 77–500 K, the magnetic susceptibility of YbZn2As2 follows the Curie–Weiss law, indicating antiferromagnetic interactions of the Yb ions and yielding a Curie temperature θ=−52.8 K and an effective magnetic moment μeff=2.35 μB (the Bohr magneton) per Yb ion. This means that a part of the Yb ions has valency 3+, instead of 2+ for all the Yb ions, as would be expected from their formal oxidation number, i.e. YbZn2As2 is a compound with mixed valency of Yb. YbZn2As2 exhibits p-type conductivity with a room temperature electrical resistivity of 0.15 Ω cm which decreases when lowering temperature and reaches a practically constant value of 0.08 Ω cm below 20 K. 相似文献
9.
The crystal structure of new ternary R3Si1.25Se7 (R = Pr, Nd and Sm) compounds (Dy3Ge1.25S7 structure type, Pearson symbol hP22.5, space group P63, a = 1.05268 (3) nm, c = 0.60396 (3) nm, RI = 0.0897 for Pr3Si1.25Se7; a = 1.04760 (3) nm, c = 0.60268 (3) nm, RI = 0.0891 for Nd3Si1.25Se7; a = 1.04166 (6) nm, c = 0.59828 (6) nm for Sm3Si1.25Se7) was determined using X-ray powder diffraction. The nearest neighbours of the R and Si atoms are exclusively Se atoms. The latter form distorted trigonal prisms around the R atoms, octahedra around the Si1 atoms and tetrahedra around the Si2 atoms. Tetrahedral surrounding exists for Se1 and Se3 atoms. Six neighbours surround every Se2 atom. 相似文献
10.
I. D. Olekseyuk L. D. Gulay I. V. Dydchak L. V. Piskach O. V. Parasyuk O. V. Marchuk 《Journal of Alloys and Compounds》2002,340(1-2):141-145
Single crystals of Cu2Zn/Cd/SnSe4 were grown using a solution-fusion method. The crystal structure of the Cu2Zn/Cd,Hg/SnSe4 compounds were investigated using X-ray powder diffraction. These compounds crystallize in the stannite structure (space group I
2m) with the lattice parameters: a=0.56882(9), c=1.13378(9) nm, c/a=1.993 (Cu2ZnSnSe4), a=0.58337(2), c=1.14039(4) nm, c/a=1.955 (Cu2CdSnSe4) and a=0.58288(1), c=1.14179(2) nm, c/a=1.959 (Cu2HgSnSe4). Atomic parameters were refined in the isotropic approximation (RI=0.0517, RI=0.0511 and RI=0.0695 for Cu2ZnSnSe4, Cu2CdSnSe4 and Cu2HgSnSe4, respectively). 相似文献
11.
Structural studies were performed for the ternary RIr3B2 compounds (R=Ce and Pr) from as cast samples. The crystal structure of the ternary boride CeIr3B2 (CeCo3B2 structure type, space group P6/mmm, a=5.520(3) Å, c=3.066(2) Å, Z=1, V=80.91 Å3, ρx=15.154 g cm−3) was refined to R1=0.0470, wR2=0.1240 from single-crystal X-ray diffraction data. The new ternary boride PrIr3B2 was found to be isostructural with the CeIr3B2 compound. Its lattice parameters a=5.5105(2) Å, c=3.1031(1) Å were obtained from a Rietveld refinement of X-ray powder diffraction data. 相似文献
12.
The new ternary compound Dy1.2Fe4Si9.8 have been prepared and studied by means of X-ray powder diffraction technique and vibrating sample magnetometer. The ternary compound Dy1.2Fe4Si9.8 crystallizes in the hexagonal Er1.2Fe4Si9.8-type structure, space group P63/mmc (no. 194) with lattice parameters a = 0.39415(1) nm and c = 1.52771(3) nm. The crystal structural refinement of the compound Dy1.2Fe4Si9.8 has been performed by using Rietveld method. Lattice thermal expansion studies on the compound were carried out in the temperature range from 298 to 1013 K. The variation of the unit cell parameters shows that the unit cell parameters increase with the increase in temperature. The coefficients of average lattice thermal expansion along various axes in the temperature range from 298 to 1013 K are , and . The temperature dependence of the magnetization for the compound was also investigated in the range from 90 to 300 K. The experimentally determined magnetic effective paramagnetic moment is μeff = 11.3μB per formula unit (10.3μB per Dy atom). 相似文献
13.
H. Samata M. Kai T. Uchida M. Ohtsuka G. Tanaka S. Sawada T. Taniguchi Y. Nagata 《Journal of Alloys and Compounds》2003,350(1-2):77-85
Crystals of Ba3NaRu2O9−δ (δ≈0.5) and Ba3(Na, R)Ru2O9−δ (R=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) were grown by an electrochemical method, and their crystallographic, magnetic, and electric properties were studied. All crystals have a hexagonal structure of space group P63mmc. Ba3NaRu2O9−δ and Ba3(Na, R)Ru2O9−δ (except Ce) have a negative asymptotic Curie temperature suggesting the existence of an antiferromagnetic order; however, they are paramagnetic at temperatures above 1.7 K. Ba3NaRu2O9−δ has an effective magnetic moment Peff of 0.91 μB, while Peff of Ba3(Na, R)Ru2O9−δ (except Ce) reflects the large free-ion moment
of the rare earth ions. Ba3(Na, Ce)Ru2O9−δ shows peculiar magnetic behavior that differs from the magnetism of other Ba3(Na, R)Ru2O9−δ crystals. The resistivity of all crystals exhibits an activation-type temperature dependence with an activation energy in the range of 0.10.2 eV. 相似文献
14.
SiC powder prepared by the Na flux method at 1023 K for 24 h and Ba were used as starting materials for synthesis of tribarium tetrasilicide acetylenide, Ba3Si4C2. Single crystals of the compound were obtained by heating the starting materials with Na at 1123 K for 1 h and by cooling to 573 K at a cooling rate of −5.5 K/h. The single crystal X-ray diffraction peaks were indexed with tetragonal cell dimensions of a = 8.7693(4) and c = 12.3885(6) Å, space group I4/mcm (No.140). Ba3Si4C2 has the Ba3Ge4C2 type structure which can be described as a cluster-replacement derivative of perovskite (CaTiO3), and contains isolated anion groups of slightly compressed [Si4]4− tetrahedra and [C2]2− dumbbells. The electrical conductivity measured for a not well-sintered polycrystalline sample was 2.6 × 10−2–7 × 10−3 S cm−1 in the temperature range of 370–600 K and slightly increased with increasing temperature. The Seebeck coefficient showed negative values of around −200 to −300 μV K−1. 相似文献
15.
Using X-ray powder and single crystal diffraction, the crystal structures of the Nd(Ru0.6Ge0.4)2 and ErRuGe compounds were investigated. The compounds belong to the KHg2 and TiNiSi type structure, respectively. 相似文献
16.
In the present paper the electric field dependence of the permittivity of (Ba, Sr)TiO3 ceramics is reported. Single phase Ba1−xSrxTiO3 (x = 0.20 and 0.30) ceramics were obtained by powders synthesized by a modified Pechini method. The dc-tunability at room temperature is higher for the ceramic with lower strontium content as this composition is ferroelectric at room temperature, whereas the composition corresponding to the higher strontium content is paraelectric. The data are well described by the Johnson's approximation for the ferroelectric state and by an additional “extrinsic” contribution due to the polar clusters in the case of the paraelectric state (Ba, Sr)TiO3 ceramic. 相似文献
17.
Ye. V. Shcherbakova G. V. Ivanova M. I. Bartashevich V. I. Khrabrov Ye. V. Belozerov 《Journal of Alloys and Compounds》1996,240(1-2):101-106
A type of magnetocrystalline anisotropy and exchange interactions of the novel ternary R3(Fe, V)29 compounds (R = Y, Nd, Sm) have been investigated. The compounds are uniaxial ferromagnets with easy magnetization direction along the [
0 1] axis of the monoclinic lattice at room temperature. The temperature variations of the magnetic moment and the first anisotropy constant for Y3(Fe, V)29 are presented. The first order magnetization process along the hard magnetization direction takes place for Sm3(Fe, V)29 at T < 120 K. A magnetic anomaly is detected in the temperature dependence of the a.c. susceptibility for Nd3(Fe, V)29 which can be related to a spin reorientation. 相似文献
18.
Neutron diffraction and magnetization measurements have been performed on the Tb5Si3 compound (hexagonal Mn5Si3-type, hP16, P63/mcm) to understand its magnetic structure and magnetic properties. The temperature-dependent neutron diffraction results prove that this intermetallic phase shows a complex flat spiral magnetic ordering, presenting three subsequent changes in magnetization at on cooling. However, the magnetization data depict two transitions at 72 K (TN1) and 55 K (TN2). The extended temperature range between and over which the neutron diffraction patterns slowly evolve might correspond to the high-temperature antiferromagnetic transition at TN1 and low-temperature antiferromagnetic transition at TN2 of the magnetic data. Between Tb5Si3 shows a flat spiral antiferromagnetic ordering with a propagation vector K1 = [0,0, ±1/4]; then, between the flat spiral type ordering is conserved, but by two coexisting propagation vectors K1 = [0,0, ±1/4] and K2 = [0,0, ±0.4644(3)]. The terbium magnetic moments arrange in the XY(ab) plane of the unit cell. Below the magnetic component with K1 = [0,0, ±1/4] vanishes and magnetic structure of Tb5Si3 is a flat spiral with K2 = [0,0, ±0.4644(3)], only. Low field magnetization measurements confirm the occurrence of complex, multiple magnetic transitions. The field dependence of the magnetization indicates a metamagnetic transition at a critical field of 3 T. 相似文献
19.
E. Wawrzy
ska B. Penc J. Hernandez-Velasco A. Szytu
a A. Zygmunt 《Journal of Alloys and Compounds》2003,350(1-2):68-71
Ho3Pd4Ge4 crystallizes in the orthorhombic Gd6Cu8Ce8-type of structure (space group Immm) in which the Ho atoms occupy two nonequivalent crystallographic positions: 2a and 4j. Neutron diffraction measurements indicate that the Ho moments in the 4j site below 6.7 K form a collinear antiferromagnetic structure with the magnetic moments parallel to the a axis, whereas the Ho moments in the 2a site below 5 K form a sine-wave modulated structure with the magnetic moments parallel to the c axis. 相似文献
20.
Cheng-Jun Duan Wei-Feng Li Jun-Lin Yuan Jing-Tai Zhao 《Journal of Alloys and Compounds》2008,458(1-2):536-541
A new compound LuBa3B9O18 has been prepared by a high-temperature solid-state reaction and its crystal structure was determined by powder X-ray diffraction methods. The results of Rietveld refinement show that it is isotypic to YBa3B9O18. The X-ray excited luminescent properties of LuBa3B9O18 were investigated. It shows a broad emission band in the wavelength range of 300–550 nm with peak center at 385 nm. Its room temperature fluorescent decay profile exhibits a single-exponent shape with decay time of 15 ns. It is believed that the lattice defects have played an important role on the luminescent performances of LuBa3B9O18 powders and its thermal luminescence measurement confirmed the existence of lattice defects in it. Considering the emission wavelength, luminescence intensity, decay time, melting point, density and non-hygroscopic property of LuBa3B9O18, one has reason to assume that it might find an application as a new scintillation material. 相似文献