Solid-state Synthesis,Crystal and Band Structures,and Optical Properties of a Novel Ternary Sulfide Eu_2Ga_2S_5

One new ternary europium gallium sulfide, Eu2Ga2S5, has been synthesized by a facile solid-state route with boron as the reducing reagent. It crystallizes in the orthorhombic space group Pbca, with a = 11.976（1）, b = 11.074（1）, c = 17.446（1）A^°, V = 1650.6（3）A^°^3, and Z = 8. Its 3-D structure is built by the connection between EuS 7 monocapped trigonal prisms and GaS 4 tetrahedra, and the latter connect with each other to form layer-like slabs. Its optical energy gap is determined to be 2.17 eV, which is also verified by the electronic band structure calculation.

Synthesis,Crystal Structure,Physical Properties and Theoretical Studies of the New Ternary Sulfide with Closed Cavities:CsYb_7S_(11)

A novel ternary rare-earth sulfide, CsYb7S（11）, has been successfully synthesized by high-temperature solid-state reaction of an elemental mixture with modified Cs Cl flux. The single-crystal X-ray diffraction data reveal its orthorhombic symmetry in space group Cmca（no. 64） with a = 15.271（3）, b = 13.414（2）, c = 18.869（3） A°, V = 3865.2（2） A°^3, Z = 8, Mr = 1696.85, Dc = 5.832 g/cm^3, μ = 36.538 mm^-1, F（000） = 5768, the final R = 0.0225 and w R = 0.0517 for 2258 observed reflections with I 〉 2σ（I）, 2.67〈θ〈27.48o, w = 1/[σ^2（Fo^2） ＋（0.0443 P）2 ＋ 8.7453 P], where P =（Fo^2 ＋ 2Fc^2）/3, S = 1.036,（Δρ）max = 1.609 and（Δρ）min = –1.922. The remarkable structural feature is the dual tricapped Cs2@S18 cube closed cavities far apart within the three-dimensional [Yb7S（11）]-covalent bonding matrix. Magnetic susceptibility measurements show that the title compound exhibits temperature-dependent（50～300 K） para-magnetism and obey the Curie-Weiss law. Moreover, the optical gap of 2.03 Ev for CsYb7S11 was deduced from the UV/Vis reflectance spectroscopy and DFT study indicates an indirect band gap with an electronic transfer excitation of S-3p to Yb-5d orbital.

Synthesis and Crystal Structure of a New Quaternary Sulfide FeSm6Si2S14

One new quaternary rare-earth sulfide, FeSm6Si2S（14）, has been synthesized by a facile solid-state route with boron as the reducing reagent. It crystallizes in the noncentrosymmetric hexagonal space group P63, belonging to the Ce6Al（3.33）S（14） structure-type, and the AxRE3MQ7 family. Its crystal structure features a 3-D framework constructed by SmS 8 bicapped trigonal prisms, where Fe and Si atoms occupy the octahedral（2a） and tetrahedral（2c） voids, respectively. The FeS 6 octahedra are connected with each other to form a chain along the b direction. FeSm6Si2S（14） represents a new chemical composition among the large family of AxRE3MQ7 compounds. The other related compounds containing transition metal are also discussed.

Crystal Structure and Magnetic Property of a Quaternary Sulfide, Al_(0.36)Sm_3Ge_(0.98)S_7

A new quaternary sulfide, Al0.36Sm3Ge0.98S7 1, has been prepared by a facile solidstate reaction, and its crystal structure was determined by single-crystal X-ray diffraction analysis. It crystallizes in the hexagonal space group P63 with a = 9.964（1）, c = 5.768（2）A, V = 495.9（1）A^3 and Z = 2. In the crystal structure of 1, Al^3＋ and Ge^4＋ occupy the octahedral and tetrahedral interspaces of the 3-D main-framework constructed by SmS8 bicapped trigonal prisms, respectively. The investigation of optical and magnetic properties of 1 indicates that its optical band gap is 2.18 eV and it shows antiferromagnetic-like interaction.

Synthesis,Crystal Structure and Optical Properties of KPr(MoO_4)_2 with the Scheelite-type Structure

Solid-state reaction of praseodymium （III） oxide,K2CO3 and MoO3 at high temperature leads to a potassium lanthanide double molybdate,namely,KPr（MoO4）2. The structural and optical properties of the title compound have been investigated by means of single-crystal X-ray diffraction and spectroscopic measurements at room temperature. KPr（MoO4）2 crystallizes in tetragonal,space group I41/a with a = 5.401（3）,c = 12.044（10）,Z = 2 and R （I 〉 2σ（I）） = 0.0416. It features the famous scheelite-type structure （CaWO4）,which can be thought as the substitution of two Ca^2＋ ions in CaWO4 by a couple of K^＋ and Pr^3＋ ions in a statistical manner,and W^6＋ by Mo^6＋ cations.

Syntheses,structures and properties of five chiral quaternary sulfides,AlxLn_3(Si_yAl_(1-γ))S_7 (Ln=Y,Gd,Dy) and In_(0.33)Sm_3SiS_7

Five new quaternary isostructural rare-earth sulfides, Al0.57Gd3(Si0.27Al0.73)S7 (1), Al0.55Dy3(Si0.34Al0.66)S7 (2), Al0.50Y3(Si0.50Al0.50)S7 (3), Al0.44Gd3(Si0.70Al0.30)S7 (4) and In0.33Sm3SiS7 (5), have been synthesized by facile solid-state reactions. They crystallize in the 3-D ALn3EQ7 structure type in the hexagonal chiral space group P63. The structures feature a 3-D host framework constructed by Ln-S bicapped trigonal prisms, in which the octahedral and tetrahedral interspaces are occupied by A and E atoms, respectively. The investigation of optical and magnetic properties of 4 indicates that it is a semiconductor and behaves antiferromagnetic-like interaction.

Syntheses and Crystal Structures of Two AlxRE3(Si1-yAly)S7(RE=Sm and Gd)Compounds

Two new quaternary rare-earth chalcogenides,Al_（0.42）Sm_3（Si_（0.74）Al_（0.26））S_7（1） and Al_（0.38）Gd_3（Si_（0.86）Al_（0.14））S_7（2）,have been synthesized by a facile solid-state route with boron as the reducing reagent.They crystallize in the noncentrosymmetric hexagonal space group P6_3,belonging to the Ce_6Al_（3.33）S_（14） structure-type.Their 3-D structures feature 3-D frameworks constructed by RES_8 bicapped trigonal prisms,and Al and Si occupy the octahedral and tetrahedral voids,respectively.Al（2） and Si（1） co-occupying the 2b site and Al（1） partially occupying the 2a site have to be considered for the stability of the structures and charge balances.The Ce_6Al_（3.33）S_（14） structure-type compounds with their rich compositions and traits are discussed.The diffuse reflectance spectrum measurement of 2 indicates that it has an energy gap of 2.13 eV.

Effect of La^(3+)substitution on structural,microstructure,magnetic properties,and microwave absorbing ability of yttrium iron garnet

Synthesis and characterization of lanthanum-doped yttrium iro n garnet(YIG)in the compositional se ries of Y_(3-x)La_(x)Fe_(5)O_(12)(x=0.0,0.1,0.3,and 0.5)were carried out.All compositions were made by using solid state reaction method with ball-milling technique.The phase formation,surface morphology,magnetic properties,and microwave absorbing ability of all compositions were characterized by using an X-ray diffractometer,a scanning electron microscope,a vibrating sample magnetometer,and a Vector network analyzer.The results reveal that all compositions are crystallized into Y_(3)Fe_(5)O_(12)phase(space group la-3d(230).It was observed that the lattice constant is increased from 1.2373 to 1.2421 nm with the increase of lanthanum substitution level from x=0.0-0.5.The crystallite size of Y_(3-x)La_(x)Fe_(5)O_(12)series calculated by Scherrer method is found to decrease from 78 nm in x=0.0-63 nm in x=0.5.The particle size distribution from the surface morphology image analysis is shifted to lower-range number with the increase of lanthanum substitution level from x=0.0 to 0.5.The substitution process also affects the lattice distortion in La-doped samples and changes the bond angles and bond lengths of the YIG structure.As the results,a linear correlation between the Fe'-O-Fe bond angle with magnetic properties parameters of saturation magnetization(M_(s))and remanence magnetization(M_(r))was studied.Due to the lanthanum substitution process,all La^(3+)-doped samples possess higher M_(s)and M_(r)values compared to the original composition.The results of Vector network analyzer show that the improvement of the M_(s)and M_(r)plays an important role in enhancing the microwave absorbing ability of the materials.The minimum RL changes from-8.22 dB(~85.22%microwave absorption)in x=0.0 to-14.21 dB(~96.25%microwave absorption)in x=0.5.The enhancement is mainly ascribed to the natural magnetic resonance loss and dipoIe-polarization loss due to the substitution process.The decreasing particle size also enhances the microwave absorbing ability of the La-doped samples via multiple-reflections mechanism.

Synthesis, characterization and dielectric properties of a novel temperature stable（1-x）CoTiNb2O8-xZnNb2O6 ceramic

(1-x)CoTiNb2O8-x ZnNb2O6 microwave dielectric ceramics were prepared via the conventional solid-state reaction route with the aim of reducing thetf value and improving the thermal stability.The phase composition and the microstructure were investigated using X-ray diffraction,Raman spectra,and scanning electron microscopy.A set of phase transitions which were induced by composition had been confirmed via the sequence:rutile structure→coexistence of rutile and columbite phase→columbite phase.For(1-x)CoTiNb2O8-x ZnNb2O6 microwave dielectric ceramics,the addition of ZnNb2O6 content(x=0–1)led to the decrease ofer from 62.98 to 23.94.As a result of the high Q×?of ZnNb2O6 ceramics,the increase of ZnNb2O6 content also led to the lower sintering temperatures and the higher Q×?values.Thetf value was reduced from+108.04(x=0)to–49.31 ppm/℃(x=1).Among them,high density 0.5CoTiNb2O8-0.5ZnNb2O6 ceramics were obtained at 1175℃with excellent microwave dielectric properties of εr 39.2,Q×? 40013 GHz,and tf+3.57 ppm/℃.

Syntheses,Structures and Band Gaps of KLnSiS_4(Ln=Sm,Yb)

Two new quaternary sulfides, KSmSiS4 （1） and KYbSiS4 （2）, have been synthesized by high-temperature solid-state reaction. Single,crystal X-ray diffraction analyses indicate that both compounds crystallize in the space group P21/m, and the crystal data are as follows： a = 6.426（11）, b = 6.582（11）, c = 8.602（15）A, β= 107.90（13）°, Z = 2, V= 346.2（10） A^3, Dc = 3.317 g/cm^3, F（000） = 318,μ（MoKα） = 10.334 mm^-1, the final R = 0.0559 and wR = 0.1370 for 1; and α= 6.3244（10）, b = 6.5552（10）, c = 8.5701（15）A, β= 108.001（13）°, Z = 2, V = 337.91（9） A^3, De= 3.621 g/cm^3, F（000） = 334, μ（MoKα） = 15.737 mm^-1, the final R = 0.0422 and wR = 0.0960 for 2. The KLnSiS4 （Ln = Sm, Yb） structure consists of corrugated ∞^2 [LnSiS4]^- layers which are formed by edge-sharing LnS8 bicapped trigonal prisms and SiS4 tetrahedra. The K^＋ cations are located in the cavities defined by S2 anions between the ∞^2[LnSiS4]^- layers. Band-gap analyses show that compounds 1 and 2 are semiconductors with optical band-gaps of 2.40 and 2.34 eV, respectively.

Dimensionality Reducing from Three-dimensional RbLu5Te8 to Two-dimensional CsMnGdTe3:Syntheses,Crystal and Electronic Structures

Two new rare-earth metal chalcogenides,namely RbLu5Te8 and CsMnGdTe3,have been successfully synthesized under high-temperature solid-state reaction conditions and structurally characterized by single-crystal X-ray diffraction analysis.RbLu5Te8 belongs to the monoclinic space group C2/m(no.12)with two formula units in a unit cell:a=22.075(5),b=4.2987(8),c=10.588(2)A,β=103.89(2)°,V=975.4(4)A3,whereas CsMnGdTe3 crystallizes in the orthorhombic space group Cmcm(no.63)with four formula units in a unit cell:a=4.4872(8),b=16.769(3),c=11.807(2)A and V=888.4(3)A3.In the structure of RbLu5Te8,face-,edgeand vertex-sharing[LuTe6]octahedra are interconnected to produce a three-dimensional(3D)framework with Rb^+lying in the tunnels.The crystal structure of CsMnGdTe3 consists of two-dimensional(2D)[MnGdTe3]^–layers of edge-and vertex-sharing[GdTe6]octahedra with Mn atoms filling the tetrahedral interstices,which stack along the b-axis.The Cs atoms are located between the[MnGdTe3]^–layers and surrounded by eight Te atoms to form a[CsTe8]bicapped trigonal prism.Moreover,theoretical studies have aided the understanding of their electronic structures.

五个无心四元硫化物AlxLn3(SiyAl1-y)S7(Ln=Y,Gd,Dy)和In0.33Sm3SiS7的合成、结构及性质

使用一种新的高温固相反应方法合成得到了五个新的异质同构的四元稀土硫化物.它们结晶于六方晶系的手性空间群P63,属于ALn3EQ7(A:碱金属或货币金属;Ln:稀土元素;E:第IVA族元素;E:硫属元素)结构类型,晶胞参数为a=9.621(1)～10.038(2),c=5.672(2)～5.939(1),V=476.1(1)～494.9(2)3,Z=2.它们的晶体结构可以描述为:LnS8双帽三棱柱之间相互连接成三维框架结构,而A位和E位原子分别占据所形成的八面体和四面体空隙.化合物4的光学和磁性质的研究表明:它是光学带隙为2.34eV的半导体,并表现出类似于反铁磁相互作用的磁行为.