Synthesis and phase formation study in K2MoO4-SrMoO4-R2(MoO4)3 systems (where R = Pr, Nd, Sm, Eu, and Gd)

Subsolidus phase formation in K₂MoO₄-SrMoO₄-R₂(MoO₄)₃ systems, where R = Pr, Nd, Sm, Eu, and Gd, in which KSrR(MoO₄)₃ triple molybdates are formed and crystallize in monoclinic crystal system (space group P2₁/n), have been studied using X-ray powder diffraction, differential thermal analysis (DTA), and vibrational spectroscopy. Unit cell parameters have been determined for these molybdates; their IR and Raman spectra are reported.     

Phase formation in the systems Rb2MoO4-BaMoO4-R2(MoO4)3, R = Nd,Sm, Eu,Gd

Phase formation in the subsolidus area of the systems Rb₂MoO₄-BaMoO₄-R₂(MoO₄)₃ was studied by the methods of X-ray and differential-thermal analysis. In these systems ternary molybdates RbBaR(MoO₄)₃ crystallizing in the monoclinic crystal system (space group P2_1/n ) are formed. Their crystallographic parameters were calculated, and temperature dependences of the electrical conduction, dielectric permeability, and dielectric loss tangent were studied.     

Crystal structure investigation of ternary molybdates Li3Ba2Ln3(MoO4)3 (Ln=Gd,Tm)

Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Institute of Physics, Siberian Branch, Russian Academy of Sciences. Buryat Institute of Natural Sciences, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 33, No. 3, pp. 126–130, May–June, 1992.     

Synthesis and electrical properties of ternary molybdates Li3Ba2R3(MoO4)8 (R = La-Lu, Y)

X-ray diffraction and differential-thermal analyses were used to study the phase relations in the subsolidus region of the system Li₂MoO₄-BaMoO₄-R₂(MoO₄)₃. The temperature dependence of the conductivity of Li₃Ba₂R₃(MoO₄)₈ phases (R = Y, Eu, Sm, La) was examined.     

Formation laws for scheelite-like triple molybdates LiMLn2(MoO4)4

The size factor is shown to be decisive in the structure formation of triple molybdates LiMLn₂(MoO₄)₄. The LiMLn₂(MoO₄)₄ compounds (where M is a large alkali metal) are formed when 0.48 Å ≤ r _M ⁺ ? r _Ln ³⁺ ≤ 0.60 Å.     

FTIR study of cerium doped electron superconductors R(1.85)Ce(0.15)CuO(4) (R=Nd, Pr, Sm, Eu and Gd)

Systematic FTIR study of electron doped compounds of the T'-series are presented in this paper. Spectroscopic techniques are more sensitive than any other technique to the disorder due to doping in the structure. Polycrystalline 'as prepared' bulk samples, allows one to observe c-axis vibrations clearly, avoiding in-plane (a-b) polarizability due to charge carriers. Even though all R(2)CuO(4)(R=Nd, Pr, Sm, Eu and Gd) doped compounds belong to T' structure, due to the different sizes of the rare earth ionic radii, the structure stabilization is very difficult to achieve since copper-oxygen distance vary from compound to compound and hence the phonon characteristic spectrum of the series. The role of apical oxygen in T-structure is discussed in detail from the point of factor group analysis and compared with the V-structure. The IR study of R(2)CuO(4) (214) compound with Ce doping reveals the difference and similarities of the electronic properties between hole doping and electron doping when compared with T-structure compounds.     

室温下合成纺锤形貌六方相NaLnF_4(Ln=Nd,Sm,Eu,Gd,Tb)纳米颗粒

室温下合成长250nm,宽100nm的纺锤形貌六方相的NaNdF4。NaEuF4,NaSmF4,NaGdF4和NaTbF4也用同样的方法获得。产物用XRD,TEM,HRTEM,FESEM和PL进行表征。PL光谱显示合成的NaEuF4的激发波长是394nm。NaEuF4有4个特征发射谱带,分别是591,615,650和681nm。     

Synthesis and crystal structure of [Ln(4-Pyta)3(H2O)2] n (Ln = Nd,Ce, Eu,Gd; 4-Pyta = 4-pyridylthioacetate)

Four new lanthanide complexes, [Nd(4-Pyta)₃(H₂O)₂] _n (1), [Ce(4-Pyta)₃(H₂O)₂] _n (2), [Eu(4-Pyta)₃(H₂O)₂] _n (3) and [Gd(4-Pyta)₃(H₂O)₂] _n (4), have been obtained from reaction of lanthanide(III) nitrate with 4-Pyta (4-pyridylthioacetate) in water. Their structures were characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction. The crystals belong to triclinic, space group P 1 and all complexes exhibit one-dimensional chains that arrange to form a three-dimensional supramolecular architecture by hydrogen bonds between the chains.     

Synthesis and structure determination of seven ternary bismuthides: crystal chemistry of the RELi3Bi2 family (RE = La–Nd,Sm, Gd,and Tb)

Zintl phases are renowned for their diverse crystal structures with rich structural chemistry and have recently exhibited some remarkable heat‐ and charge‐transport properties. The ternary bismuthides RELi₃Bi₂ (RE = La–Nd, Sm, Gd, and Tb) (namely, lanthanum trilithium dibismuthide, LaLi₃Bi₂, cerium trilithium dibismuthide, CeLi₃Bi₂, praseodymium trilithium dibismuthide, PrLi₃Bi₂, neodymium trilithium dibismuthide, NdLi₃Bi₂, samarium trilithium dibismuthide, SmLi₃Bi₂, gadolinium trilithium dibismuthide, GdLi₃Bi₂, and terbium trilithium dibismuthide, TbLi₃Bi₂) were synthesized by high‐temperature reactions of the elements in sealed Nb ampoules. Single‐crystal X‐ray diffraction analysis shows that all seven compounds are isostructural and crystallize in the LaLi₃Sb₂ type structure in the trigonal space group Pm1 (Pearson symbol hP6). The unit‐cell volumes decrease monotonically on moving from the La to the Tb compound, owing to the lanthanide contraction. The structure features a rare‐earth metal atom and one Li atom in a nearly perfect octahedral coordination by six Bi atoms. The second crystallographically unique Li atom is surrounded by four Bi atoms in a slightly distorted tetrahedral geometry. The atomic arrangements are best described as layered structures consisting of two‐dimensional layers of fused LiBi₄ tetrahedra and LiBi₆ octahedra, separated by rare‐earth metal cations. As such, these compounds are expected to be valance‐precise semiconductors, whose formulae can be represented as (RE³⁺)(Li¹⁺)₃(Bi³⁻)₂.     

聚合物裂解法制备稀土铁氧体LnFeO_3(Ln=Pr,Sm,Eu,Gd)纳米晶

以丙烯酸和稀土离子为原料,经原位聚合裂解法合成聚合物前驱体[1Ln(Ln=Pr,Sm,Eu,Gd)];1Ln在空气氛中于500℃热解3 h制得4个稀土铁氧体纳米晶[Ln Fe O3(2Pr~2Gd)],其结构和形貌经FT-IR,TGA,XRD和SEM确证。     

白光LED用红色发射荧光粉Gd2(MoO4)3:Eu3+制备与表征

以NH4F为助熔剂采用固相反应法合成了Eu^3＋掺杂的α—Gd2（MoO4）3荧光粉。研究了引入不同含量助熔剂时对材料的结晶、荧光粉颗粒粒径、表面形貌及光谱性质的影响。实验结果表明,引入重量比为3％时样品具有好的结晶和优良的光谱性质;同时,随着助熔剂量的增加Eu^3＋离子在晶体中所处的格位对称性发生了变化;另外,通过Eu^3＋掺杂浓度变化的结果讨论了Eu^3＋的浓度猝灭行为。光谱测量的结果表明,该荧光粉与其他商品荧光粉不同,其最有效的激发波长不在电荷迁移带范围,而是465和395nm跃迁,该荧光粉可作为近紫外LED和三基色荧光粉组合型自光器件的红色荧光粉的候选材料。     

RE2CuO4的热力学稳定性（RE=La,Nd,Sm,Eu）

构筑了ＭｇＯ部分稳定的ＺｒＯ２基固体电解质电化学电池测量ＥＡＦ的实验装置，测定了Ｓｍ２ＣｕＯ４的标准Ｇｉｂｂｓ生成自由能。结果表明化合物ＲＥ２ＣｕＯ２３（ＲＥ＝Ｌａ，Ｎｄ，Ｓｍ，Ｅｕ）随着镧系元素离子半径减小，热力学稳定性下降，并用晶体场理论解释了这一规律。     

Synthesis of ternary potassium,magnesium, and zirconium molybdates. The crystal structure of K5(Mg0.5Zr1.5)·(MoO4)6

Three (5∶1∶3, 1∶1∶1, and 2∶1∶6) ternary phases were discovered in the K₂MoO₄?AMoO₄?Zr(MoO₄)₂ system, where A is Mg or Mn. For A=Mg, we have synthesized 5∶1∶3 single crystals and determined their crystal structure from X-ray diffraction data (a CAD-4 automatic diffractometer, MoK_α radiation, 1166 F(hkl), and R=0.026). The compound crystallizes in the trigonal system with space group R3c, a=10.576(1), c=37.511(3), Å, Z=6, d_calc=3.576, and d_msd=3.54 g/cm³. The structure is a three-dimensional composite framework of alternating Mo tetrahedra and (Mg, Zr) octahedra, which are linked via the common O vertices. Potassium atoms of three kinds are located in large framework cavities. Their polyhedra (ten-vertex polyhedra and a cubeoctahedron) are linked together by common faces and edges to form infinite zigzag columns of a large section. When solving the structure, we refined the composition of the crystals and the distribution of Mg²⁺ and Zr⁴⁺ cations in the M(1) and M(2) positions resulting in the formula above.     

Calculation of Ln-Ba (Ln = Gd,Pr, Nd,and Sm) phase diagrams

A thermodynamic model of liquid was suggested and Ln-Ba (Ln = Gd, Pr, Nd, and Sm) phase diagrams were calculated on the basis of generalization of literature data on thermodynamic properties and phase equilibria in lanthanide-barium metallic systems. The interaction parameter of Gd_{1 ? x} Ba _x regular melt was estimated on the assumption of a proportionality between the particle-particle interaction energies of liquid lanthanide and liquid barium, on the one hand, and the lanthanide radius, on the other.     

Electrical resistivity of pyrochlore compounds R2Mo2O7(R =Nd,Sm, Gd,Tb, Y)

The electrical resistivity ofR₂Mo₂O₇(R =Nd, Sm, Gd, Tb, Y) pyrochlores was measured in the temperature range 4.2 to 300 K. Metallic behavior is observed for Nd₂Mo₂O₇, Sm₂Mo₂O₇, and Gd₂Mo₂O₇ which have relatively high magnetic ordering temperatures due to ferromagnetism on the molybdenum sublattice. A clear drop in resistivity is observed near the magnetic ordering point for all metallic materials. A resistance minimum observed at low temperatures, which may be due to the magnetic ordering of the rare-earth sublattice, is not completely understood. Tb₂Mo₂O₇ and Y₂Mo₂O₇, which show no molybdenum sublattice ordering down to 4.2 K, are semiconductors. However, the temperature dependence of the resistivity is not exponential. This unusual resistivity behavior is typical of degenerate semiconductors.     

Hydrothermal preparation,structures, and NLO properties of the rare earth molybdenyl iodates,RE(MoO2)(IO3)4(OH) [RE = Nd,Sm, Eu

The reactions of RE(IO3)3 [RE = Nd, Sm, Eu] with I2O5 and MoO3 in a 1:2:2 molar ratio at 200 degrees C in aqueous media provide access to RE(MoO2)(IO3)4(OH) [RE = Nd (1), Sm (2), Eu (3)] as pure phases as determined from powder X-ray diffraction data. Single crystal X-ray diffraction experiments demonstrate that these compounds are isostructural and crystallize in the chiral and polar space group P2(1). The structures are composed of three-dimensional networks formed from eight-coordinate, square antiprismatic RE3+ cations and MoO2(OH)+ moieties that are bound by bridging iodate anions. The Mo(VI) centers are present in distorted octahedral environments composed of two cis-oxo atoms, a hydroxo group, and three bridging iodate anions arranged in a fac geometry. There are four crystallographically unique iodate anions in the structures of 1-3, one of these is actually present in the form of a IO3+1 polyhedron where a short interaction of 2.285(4) A is formed between the iodate anion and the hydroxo group bound to the Mo(VI) center. This interaction results in significant distortions of the iodate anion similar to those found in tellurites with TeO3+1 units. Two of the four iodate anions are aligned along the polar b-axis, imparting the required polarity to these compounds. Second-harmonic generation (SHG) measurements on sieved powders of 1 show a response of 350 x alpha-quartz. Crystallographic data: 1, monoclinic, space group P2(1), a = 6.9383(5) A, b = 14.0279(9) A, c = 7.0397(5) A, beta = 114.890(1) degrees, Z = 2; 2, monoclinic, space group P2(1), a = 6.9243(6) A, b = 13.963(1) A, c = 7.0229(6) A, beta = 114.681(1) degrees, Z = 2; 3, monoclinic, space group P2(1), a = 6.9169(6) A, b = 13.943(1) A, c = 7.0170(6) A, beta = 114.542(1) degrees, Z = 2.     

Binary molybdates K4M2+(MoO4)3 (M2+=Mg, Mn, Co) and crystal structure of K4Mn(MoO4)3

Binary molybdates K₄M²⁺ (MoO₄)₃ (M²⁺=Mg, Mn, Co) isostructural to triclinic \ga-K₄Zn(WO₄)₃ were synthesized, and optimal conditions for their spontaneous crystallization were found. It was established by XRPA and DTA that at 530°C the structure of the compound with cobalt undergoes a transition to the orthorhombic structure of K₄Zn(MoO₄)₃. The structure of K₄Mn(MoO₄)₃ was determined from single crystal diffraction data (a=7.613, b=9.955, c=10.156 Å,α=92.28,β=106.66,γ=105.58°, Z=2, space group $P\bar 1$ , R=0.030). In this compound, Mn has a higher coordination number (CN=5+1) than that of Zn inα-K₄Zn(WO₄)₃ (CN=4+1). The main structural feature is pairs of MnO₆ octahedra linked by the bridging MoO₄ tetrahedra into ribbons stretching along the a axis. The structure is compared with related structures of binary molybdates and other members of the alluaudite family.     

Assisted Self-Assembly to Target Heterometallic Mn-Nd and Mn-Sm SMMs: Synthesis and Magnetic Characterisation of [Mn7Ln3(O)4(OH)4(mdea)3(piv)9(NO3)3] (Ln=Nd,Sm, Eu,Gd)**

In an assisted self-assembly approach starting from the [Mn₆O₂(piv)₁₀(4-Me-py)₂(pivH)₂] cluster a family of Mn−Ln compounds (Ln=Pr−Yb) was synthesised. The reaction of [Mn₆O₂(piv)₁₀(4-Me-py)₂(pivH)₂] ( 1 ) with N-methyldiethanolamine (mdeaH₂) and Ln(NO₃)₃ ⋅ 6H₂O in MeCN generally yields two main structure types: for Ln=Tb−Yb a previously reported Mn₅Ln₄ motif is obtained, whereas for Ln=Pr−Eu a series of Mn₇Ln₃ clusters is obtained. Within this series the Gd^III analogue represents a special case because it shows both structural types as well as a third Mn₂Ln₂ inverse butterfly motif. Variation in reaction conditions allows access to different structure types across the whole series. This prompts further studies into the reaction mechanism of this cluster assisted self-assembly approach. For the Mn₇Ln₃ analogues reported here variable-temperature magnetic susceptibility measurements suggest that antiferromagnetic interactions between the spin carriers are dominant. Compounds incorporating Ln=Nd^III( 2 ), Sm^III( 3 ) and Gd^III ( 5 ) display SMM behaviour. The slow relaxation of the magnetisation for these compounds was confirmed by ac measurements above 1.8 K.     

Synthesis and crystal structural study of ternary molybdate NaMg3In(MoO4)5

We have synthesized single crystals of a temary molybdate NaMg₃In(MoO₄)₅ and cam'ed out an X-ray structural study (a KM-4 automatic difiactometer, MoK, radiation, 4503 F, R = 0.047). The triclinic unit cell dimensions are a = 7.0476(7), b = 17.935(2), c = 6.9849(7)Å, = 87.650(9), = 100.980(8), = 92.510(9)°, V= 865.5(2) A³, Z = 2, and space group P^–1. The crystal structure involves MoO₄ tetrahedra and (Mg, In)0₆ octahedra forming a three-dimensional framework with Na atoms located in its cavities. The compound melts at 990°C with decomposition.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Institute of Physics, Siberian Branch, Russian Academy of Sciences. Buryatian Institute of Natural Sciences, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 5, pp. 147–151, September–October, 1993.Translated by T. Yudanova