Nd3+, Eu3+, and Gd3+ ions as local probes in the NaxSr3−2xLnx(PO4)2 and KCaLn(PO4)2 rare earth phosphates

Use of Nd³⁺, Eu³⁺, and Gd³⁺ as local structural probes allows the determination of the rare earth positions in the Na_xSr_3?2xLn_x(PO₄)₂ (Ln = La to Tb) and KCaLn(PO₄)₂ phases (Ln = rare earth). Moreover, a common feature of both series is a particularly high splitting of the excitation ${}^6\text{P}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ and ${}^6\text{P}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ levels of the Gd³⁺ ions.     

Ln(GaM2+)O4 and Ln(AlMn2+)O4 compounds having a layer structure [Ln = Lu,Yb, Tm,Er, Ho,and Y,and M = Mg,Mn, Co,Cu, and Zn]

A series of new compounds Ln(GaM²⁺)O₄ and Ln(AlMn²⁺)O₄ having a layer structure were successfully prepared [Ln = Lu, Yb, Tm, Er, Ho, and Y, and M = Mg, Mn, Co, Cu, and Zn]. The synthesis conditions and the unit cell parameters for 23 compounds have been determined. These compounds are isostructural with YbFe₂O₄ (space group $\text{R}\text{3}\text{m, a = 3.455(1)}$ Å, and c = 25.109(2) Å).     

Electrical conductivity of Th3P4-type EnLn2S4

Electrical conductivity measurements of Th₃P₄-type EuLn₂S₄ (Ln = LaGd) compounds have been made as functions of temperature and sulfur vapor pressure. These compounds are all p-type semiconductors, and their conductivities at room temperature have almost the same values for the specimens from EuLa₂S₄ to EuNd₂S₄ but increase on going from EnNd₂S₄ to EuGd₂S₄. In addition, the conductivity of EuGd₂S₄ is sensitive to sulfur vapor pressure and obeys the relationship . The mechanism of electrical transport in these compounds is discussed.     

Structure cristalline du phosphatoantimonate K3Sb3P2O14

K₃Sb₃P₂O₁₄ crystallizes in the rhombohedral system, space group $\text{R}\text{3}\text{m}$ with a = 7.147(1) Å, c = 30.936(6) Å, Z = 3. The structure was determined from 701 reflections collected on a Nonius CAD4 automatic diffractometer with $\text{Mo}\text{K}\text{α}$ radiation. The final R index and the weighted R_w index are 0.033 and 0.042, respectively. The structure is built up from layers of SbO₆ octahedra and PO₄ tetrahedra sharing corners. The potassium ions are situated between the (Sb₃P₂O₁₄)^3? covalent layers.     

Refined cell parameters of the Ln2WO6-type rare earth tungstates

Rare earth tungstates of the stoichiometry Ln₂WO₆ where Ln = Ce to Lu have been prepared and their lattice parameters were refined by a least-squares method. They have two structures: the $\text{C}\text{2}\text{c}$ symmetry for the compositions Ce₂WO₆ through Ho₂WO₆, and a monoclinic group from Er₂WO₆ to Lu₂WO₆ crystallizing most likely in the $\text{P}\text{2}\text{m}$ or $\text{P2}{}_1\text{m}$ structure. High pressure modifications are described for Dy₂WO₆ and Ho₂WO₆.     

Single-crystal growth and structure determination of Ag16I12P2O7

Single crystals of the fast-ion conductor Ag₁₆I₁₂P₂O₇ were prepared and their structure ($\text{P6}\text{mcc}\text{, a = 12.054, c = 7.504}$ Å) was determined by X-ray diffraction (r = 0.08). The I atoms form a close-packed array leaving channels occupied by P₂O^4?₇ ions running along the c axis. The Ag atoms are disordered over four different types of site with occupation numbers ranging from 0.12 to 0.52. Each Ag⁺ ion coordination polyhedron shares several faces with adjacent polyhedra providing ready paths for Ag⁺ ion conduction.     

Les phases SrLnMnO4 (Ln = La,Nd, Sm,Gd), BaLnMnO4 (Ln = La,Nd) et M1+xLa1−xMnO4 (M = Sr,Ba)

The phases SrLnMnO₄ (Ln = La, Nd, Sm, Gd), BaLnMnO₄ (Ln = La, Nd) and the solid solutions M_1+xLa_1?xMnO₄ (M = Sr: 0 ? x ? 1; M = Ba: 0 ? x ? 0.50) have a K₂NiF₄-type structure. The $\text{c}\text{a}$ ratio of the unit cell is related to the electronic configuration of the Mn³⁺ ions.     

Synthèse et caractéristiques cristallographiques des phases solides de type fluorine des systèmes PbF2LnF3

A preliminary study of the PbF₂LnF₃ systems (Ln = lanthanides and Y) has allowed the characterisation of three phases: a disordered fluorite-like solid solution Pb_1?xLn_xF_2+x the domain of which increases with increasing temperature and dopant ion radius, and two anion-excess fluorite related superstructures: Pb₂YF₇ (tetragonal, space group I4 or $\text{I4}\text{m}\text{, a \#}\text{a}{}_{\mathrm{<mtext>F</mtext>}}\text{√2}\text{, c \# 3a}{}_{\mathrm{<mtext>F</mtext>}}$) and Pb₄Ln₃F₁₇ with Ln = SmLu (rhombohedral, space group $\text{R3, a}{}_{\mathrm{<mtext>h</mtext>}}\text{\# (}\text{a}{}_{\mathrm{<mtext>F</mtext>}}\text{√2}\text{)√7, c}{}_{\mathrm{<mtext>h</mtext>}}\text{\# 2a}{}_{\mathrm{<mtext>F</mtext>}}\text{√3}$). The crystallographic characteristics of the two ordered phases have been confirmed by electron diffraction.     

The crystal structure of hexathallium(I) hexatellurodigermanate(III), Tl6[Ge2Te6]

The new compound Tl₆[Ge₂Te₆] was prepared by thermal synthesis from the elements. The material is triclinic, space group $\text{P}\text{1}$, with a = 9.471(2), b = 9.714(2), c = 10.389(2) Å, α = 89.39(1), β = 97.27(1), γ = 100.79(1)°, and Z = 2. The crystal structure was determined from single-crystal intensity data measured by means of an automated four-circle diffractometer and refined to an R value of 0.053 for 1831 observed reflections. Tl₆[Ge₂Te₆] is characterized by Ge₂Te₆ units with GeGe bonds which are linked into a three-dimensional structure by Tl atoms coordinated to essentially six Te atoms. The most important mean distances are $\text{d}\text{GeGe}\text{) = 2.456}$ Å, $\text{d}\text{(}\text{GeTe}\text{) = 2.573}$ Å, and $\text{d}\text{(}\text{TlTe}\text{) = 3.515}$Å. The lone 6s electron pairs of the thallium(I) atoms exhibit significant stereochemical activity. Tl₆[Ge₂Te₆] represents a new structure type.     

Substitution in barium-fluoride apatite: The crystal structures of Ba10(PO4)6F2, Ba6La2Na2(PO4)6F2 and Ba4Nd3Na3(PO4)6F2

The crystal structures of the apatites Ba₁₀(PO₄)₆F₂(I), Ba₆La₂Na₂(PO₄)₆F₂(II) and Ba₄Nd₃Na₃(PO₄)₆F₂ (III) have been determined by single-crystal X-ray diffraction. All three compounds crystallize in a hexagonal apatite-like structure. The unit cells and space groups are: I, a = 10.153(2), c = 7.733(1)Å, $\text{P6}{}_3\text{m}\text{; a = 9.9392(4), c = 7.4419(5)}$Å, $\text{P}\text{6}$; III, a = 9.786(2), c = 7.281(1)Å, $\text{P}\text{3}$. The structures were refined by normal full-matrix crystallographic least squares techniques. The final values of the refinement indicators R_w and R are: I, R_w = 0.026, R = 0.027, 613 observed reflections; II, R_w = 0.081, R = 0.074, 579 observed reflections; III, R_w = 0.062, R = 0.044, 1262 observed reflections.In I, the Ba(1) atoms located in columns on threefold axes, are coordinated to nine oxygen atoms; the Ba(2) sites form triangles about the F site and are coordinated to six oxygen atoms and one fluoride ion. The fluoride ions are statistically displaced ～0.25 Å from the Ba(2) triangles. This displacement of the F ions is analogous to the displacement of OH ion in Ca₁₀(PO₄)₆(OH)₂.The structures of II and III contain disordered cations. In II there is disorder between La and Na in the column cation sites as well as triangle sites. In III, Nd and Na ions are ordered in the column sites, but there is disorder among Ba and the remaining Nd and Na ions in the triangle sites to give an average site population of $\text{2}\text{3}\text{Ba}\text{,}\text{1}\text{6}\text{Nd}\text{,}\text{1}\text{6}\text{Na}$. The coordination of the rare earth ions and Na ions in the ordered column sites are nine and six oxygens, respectively, in accord with the greater charge of the rare earth ions as compared with Na. The F ions in both II and III suffer from considerable disorder in position, and their locations are not precisely known.     

KxP2W2O16: A bronze with a tunnel structure built up from PO4 tetrahedra and WO6 octahedra

The structure of a $\text{K}{}_{\mathrm{x}}\text{P}{}_2\text{W}{}_4\text{O}{}_{16}\text{(x ? 0.4)}$ crystal was established by X-ray analysis. The solution in the cell of symmetry $\text{P2}{}_1\text{m}$, with a = 6.6702(5), b = 5.3228(8), c = 8.9091(8) Å, β = 100.546(7)°, Z = 1, has led to R = 0.033 and R_w = 0.036 for 2155 reflections with $\text{σ(I)}\text{I}\text{≤ 0.333}$. This structure can be described as two octahedra-wide ReO₃-type slabs connected through “planes” of PO₄ tetrahedra. A new structural family K_xP₂W_2nO_6n+4 can be foreseen which is closely related to the orthorhombic P₄W₈O₃₂ and the monoclinic Rb_xP₈W_8nO_24n+16 series.     

Crystal structure of Fe2P2O7

Fe₂P₂O₇ crystallizes in the $\text{C}\text{1}$ space group with lattice parameters a = 6.649(2)Å, b = 8.484(2)Å, c = 4.488(1)Å, α = 90.04°, β = 103.89(3)°, γ = 92.82(3)°, and ?_cal = 3.86 g/cc. It is essentially isostructural with β-Zn₂P₂O₇. As in the Zn compound, the bridging oxygen atom in the P₂O₇ group shows a high anisotropic thermal motion. It appears that the P-O-P bond angle is linear as a result of extensive π bonding with the p orbitals on the bridging oxygen atom. The high thermal motion is vibration of the atom into cavities in the structure.     

Une nouvelle famille structurale: Les oxydes Ln4−2xBa2+2xZn2−xO10−2x (Ln = La,Nd)

Two original compounds, Ln_4?2xBa_2+2xZn_2?xO_10?2x, were isolated for Ln = La, Nd and 0 ≤ x ≤ 0.25. These oxides are tetragonal with a and c parameters close to 6.91 and 11.59 Å, respectively, for lanthanum, and 6.75 and 11.54 Å for neodymium. The structure of these phases was determined from X-ray powder patterns in the most symmetric space group, $\text{I}\text{4}\text{mcm}$, using Patterson and Fourier functions for x = 0. The structure should be compared to that of copper oxides La_4?2xBa_2+2xCu_2?xO_10?2x: it is built up of identical Ln₂O₅ layers formed from face- and edge-sharing LnO₈ polyhedra, between which Ba²⁺ and Zn²⁺ ions are inserted. Contrary to the copper compounds, two successive Ln₂O₅ layers are rotated by 90°, involving a doubling of c. The result for Zn²⁺ is tetrahedral coordination, while the coordination of Ba²⁺ becomes a bicapped antiprism.     

Structure and luminescence of the α-LnNb3O9-type rare earth niobates

α-LnNb₃O₉ (Ln = La, Pr, Nd) compounds have been prepared hydrothermally from acidic solutions. In comparison to the previously reported orthorhombic β modifications, α-LnNb₃O₉ compounds are monoclinic. The structure of α-PrNb₃O₉ was determined with a = 5.3784(6), b = 7.602(2), c = 16.344(2) Å, and β = 92.21(1)°, space group $\text{P2}{}_1\text{c}$. It is built of double and single chains of corner-shared NbO₆ octahedra extended along the b axis. Praseodymium atoms reside in tunnels along the b axis and are in eight-coordination with oxygen. All α-LnNb₃O₉ compounds can be irreversibly converted to the β modification by heating in air to 1200°C. The X-ray excited luminescence of Sm-, Eu-, Tb-, and Dy-doped α-LaNb₃O₉ is also reported.     

X-ray study of Hg2Cl2Br2 and HgCl2HgBr2 reactions in solid state

The reactions (I) Hg₂Cl₂(s) + Br₂(g) and (II) HgCl₂(s) + HgBr₂(s) have been investigated by an X-ray method. Both the reactions yield two forms of the mixed halide HgClBr, designated as α-HgClBr and β-HgClBr. The cell parameters of the two are as follows:α-HgClBr: $\text{a = 6.196}\text{A}\text{?}$, $\text{b = 13.12}\text{A}\text{?}$, $\text{c = 4.37}\text{A}\text{?}$, z = 4, ? = 5.91 g/cm³. The powder pattern and cell parameters are similar to that of HgCl₂. Therefore it is probable that the chlorine atoms, in the linear halogenHghalogen molecules of HgCl₂ structure have been replaced by bromines, and since the radius of the bromine atom is larger than that of chlorine, the lattice is larger in this case.β-HgClBr: $\text{a = 6.78}\text{A}\text{?}$, $\text{b = 13.175}\text{A}\text{?}$, $\text{c = 4.17}\text{A}\text{?}$, z = 4, ? = 5.40. These parameters are the same as those reported in the literature for β-Hg(ClBr)₂, and its X-ray powder pattern is similar to HgCl₂. Therefore this phase also has linear halogenHghalogen molecules but the distribution of Cl and Br atoms is perhaps random.Heating the products (I) and (II) up to the melting point increases the amount of α phase and decreases the β phase, whereas crystallization increases the β phase. DTA study has supported the X-ray findings.     

The crystal structure of Sc2Ru5B4

The crystal structure of Sc₂Ru₅B₄ has been determined by single-crystal X-ray analysis. Sc₂Ru₅B₄ crystallizes in the primitive monoclinic space group $\text{P2}\text{m}$ with a = 9.983(6), b = 8.486(4), c = 3.0001(3)Å, γ = 90.01(7)°, Z = 2. Deviations from the orthorhombic space group Pbam-D⁹_2h are small but significant. Intensity measurements were obtained from a four-circle diffractometer. The structure was solved by Patterson methods and refined by full matrix least-squares calculation. $\text{R =}\text{∑|ΔF|}\text{∑|F}{}_0\text{|}\text{= 0.036}$ for an asymmetric set of 863 independent reflections (|F₀|>2σ(F₀)). The crystal structure is characterized by two different types of boron atoms: (a) isolated borons B(1) and B(3) in distorted trigonal Ru-prisms with tetrakaidekahedral metal coordination: 6Ru + 3Sc, and (b) boron atoms B(2) and B(4) with a pronounced tendency to form boron pairs (B(2)-B(2) = 1.86 Å, B(4)-B(4) = 1.89 Å); the metal coordination of these boron atoms is 6Ru + 2Sc. Sc atoms have a coordination number of 17 consisting of 10Ru + 2Sc + 5B. The crystal structure of Sc₂Ru₅B₄ is a pentagon layer structure (Ru, B atoms) with a 4.3.4.3²-secondary layer of Sc atoms. The structure is furthermore related to the structure types of Ti₃Co₅B₂ and CeCo₃B₂. From powder photographs Sc₂Os₅B₄ is isotypic. No superconductivity was observed for Sc₂(Ru, Os)₅B₄ down to 1.5 K.     

Crystal structure of a barium-zinc decametaphosphate Ba2Zn3P10O30

Barium-zinc decametaphosphate, Ba₂Zn₃P₁₀O₃₀, is monoclinic, $\text{P2}\text{n}$, with the unit cell parameters a = 21.738(15), b = 5.356(5), c = 10.748(8) Å, β = 99.65(3)° and Z = 2. The crystal structure was solved with a final R value of 0.041. This salt provides the first structural evidence for the existence of a 10-phosphorus ring anion.     

Synthesis and structural study of the new rare earth magnesium borates LnMgB5O10 (Ln = La, …, Er)

To obtain rare earth luminescent materials with weak concentration quenching, the B₂O₃-rich portion of the ternary diagram Ln₂O₃MgOB₂O₃ (Ln = rare earth) has been investigated. A ternary phase of composition LnMgB₅O₁₀ has been found for Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er. These compounds all crystallize in the monoclinic space group $\text{P2}{}_1\text{c}$. The structure has been determined on a LaMgB₅O₁₀ crystal. A full-matrix least-squares refinement leads to R = 0.039. The structure can be described as being made of (B₅O₁₀^5?)_n two-dimensional layers linked together by the lanthanum and magnesium ions. The rare earth atom coordination polyhedra form isolated chains. These borates are isostructural with some rare earth cobalt borates.     

Polyèdre de coordination de l'etain(II) dans SnC2O4: Relations structurales entre SnC2O4, Na2C2O4 et Na2Sn(C2O4)2

The crystal structure of SnC₂O₄ has been determined by X-ray single-crystal techniques and refined to R = 0,018 for 1139 reflections. The cell is monoclinic, space group $\text{C2}\text{c}$ with Z = 4 formula units, the parameters being a = 10,375(3)Å. b = 5,504(2)Å, c = 8,234(3)Å, β = 125,11(2)°. The oxalato groups, located on symmetry centers, are chelated to two Sn atoms through one oxygen on each carbon atom, giving rise to an infinite string (SnC₂O₄)_n. The Sn(II) atom is one-side bonded to four oxygen atoms with two SnO bonds of 2,232(2) Å and two of 2,393(2) Å. The tin atom is in a distorted trigonal bipyramid SnO₄E, the lone pair E occupying one of the apices of the equatorial trigonal base of the polyhedron. Crystal structure comparison with disodium bisoxalatostannate(II), Na₂Sn(C₂O₄)₂, permits one to deduce SnC₂O₄ by crystallographic shear operation $\text{1}\text{8}\text{[34}\text{2}\text{](001)}$ of $\text{c}\text{2}$ periodicity. Na₂Sn(C₂O₄)₂ can be described as an intergrowth of SnC₂O₄ and Na₂C₂O₄ structures and consldered as the first member of a new series Na₂Sn_1+n(C₂O₄)_2+n with n integer ? 0.     

Reaction of some tertiary phosphines and phosphites with [Co(η5-C5H5)(S2C2{CN}2)]

Reaction of the 16 electron monomer [Co(η⁵-C₅H₅)(S₂C₂{CN}₂)] with various tertiary phosphines and phosphites (L) gives readily the 18 electron monomers [Co(η⁵-C₅H₅)(S₂C₂{CN}₂)L] which for L = P(OR)₃ have J($\text{P}$C₅$\text{H}$₅) ca. 6 Hz but J($\text{P}$C₅$\text{H}$₅) = 0 for L = PR₃.