REAuAl4Ge2 and REAuAl4(AuxGe1−x)2 (RE=rare earth element): Quaternary intermetallics grown in liquid aluminum

The two families of intermetallic phases REAuAl₄Ge₂ (1) (RE=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm and Yb) and REAuAl₄(Au_xGe_1−x)₂ (2) (x=0.4) (RE=Ce and Eu) were obtained by the reactive combination of RE, Au and Ge in liquid aluminum. The structure of (1) adopts the space group R-3m (CeAuAl₄Ge₂, , ; NdAuAl₄Ge₂, , ; GdAuAl₄Ge₂, , ; ErAuAl₄Ge₂, , ). The structure of (2) adopts the tetragonal space group P4/mmm with lattice parameters: , for EuAuAl₄(Au_xGe_1−x)₂ (x=0.4). Both structure types present slabs of “AuAl₄Ge₂” or “AuAl₄(Au_xGe_1−x)₂” stacking along the c-axis with layers of RE atoms in between. Magnetic susceptibility measurements indicate that the RE atoms (except for Ce and Eu) possess magnetic moments consistent with +3 species. The Ce atoms in CeAuAl₄Ge₂ and CeAuAl₄(Au_xGe_1−x)₂ (x=0.4) appear to be in a mixed +3/+4 valence state; DyAuAl₄Ge₂ undergoes an antiferromagnetic transition at 11 K and below this temperature exhibits metamagnetic behavior. The Eu atoms in EuAuAl₄(Au_xGe_1−x)₂ (x=0.4) appear to be in a 2+ oxidation state.     

Long-range magnetic ordering of S=1/2 linear trimers in A3Cu3(PO4)4 (A=Ca, Sr, and Pb)

Magnetic properties of S=1/2 linear trimer cluster compounds A₃Cu₃(PO₄)₄ (A=Ca, Sr, and Pb) were investigated. Magnetic susceptibility data for the three compounds showed that paramagnetic copper spins form trimers with the total spin of 1/2 below about 45 K. Specific heat and magnetization measurements indicated that the trimer clusters undergo ferromagnetic long-range ordering at for A=Ca and antiferromagnetic long-range ordering at for A=Sr and for A=Pb. A₃Cu₃(PO₄)₄ exhibited 1/3-magnetization plateau at least up to magnetic field of 55 T at 1.3 and 4.2 K. A₃Cu₃(PO₄)₄ with A=Sr and Pb showed a spin-flop transition near 0.03 T in the antiferromagnetic state at 0.08 K. Specific heat data at magnetic fields clearly showed broad maxima at low temperatures due to the finite intra-chain interaction in one-dimensional arrays of the trimers.     

High-pressure synthesis and single-crystal structure refinement of gadolinium holmium silicate hydroxyapatite Gd4.33Ho4.33(SiO4)6(OH)2

Single crystals of gadolinium holmium silicate hydroxyapatite Gd_4.33Ho_4.33(SiO₄)₆(OH)₂ have been synthesized at 2.0 GPa and 1450 °C using a piston-cylinder-type high-pressure apparatus. The crystal symmetry by single-crystal X-ray diffraction analysis is hexagonal, space group P6₃/m (No. 176), with a=9.3142(5) Å, c=6.7010(4) Å, Z=1. Gadolinium and Ho are disordered over the two large cation positions, A(1) and A(2), and charge balance in this silicate apatite is maintained by cation vacancies in A(1). Two other apatite-structure crystals investigated have and Imma symmetry, and represent either partially ordered Gd-Ho distributions or crystal strain induced during quenching.     

Layered ruthenium hexagonal perovskites: The new series [Ba2Br2−2x(CO3)x][Ban+1RunO3n+3] with n=2, 3, 4, 5

Single crystals of the title compounds were prepared by solid state reactions from barium carbonate and ruthenium metal using a BaBr₂ flux and investigated by X-ray diffraction method using Mo(Kα) radiation and a Charge Coupled Device (CCD) detector. A structural model for the term n=2, Ba₅Ru₂Br₂O₉ (1) was established in the hexagonal symmetry, space group P6₃/mmc, a=5.8344(2) Å, c=25.637(2) Å, Z=2. Combined refinement and maximum-entropy method (MEM) unambiguously show the presence of CO₃²⁻ ions in the three other compounds (2, 3, 4). Their crystal structures were solved and refined in the trigonal symmetry, space group , a=5.8381(1) Å, c=15.3083(6) Å for the term n=3, Ba₆Ru₃Br_1.54(CO₃)_0.23O₁₂ (2), and space group , a=5.7992(1) Å, c=52.866(2) Å and a=5.7900(1) Å, c=59.819(2) Å for the terms n=4, Ba₇Ru₄Br_1.46(CO₃)_0.27O₁₅ (3), and n=5, Ba₈Ru₅Br_1.64(CO₃)_0.18O₁₈ (4), respectively. The structures are formed by the periodic stacking along [0 0 1] of (n+1) hexagonal close-packed [BaO₃] layers separated by a double layer of composition [Ba₂Br_2−2x(CO₃)_x]. The ruthenium atoms occupy the n octahedral interstices created in the hexagonal perovskite slabs and constitute isolated dimers Ru₂O₉ of face-shared octahedra (FSO) in 1 and isolated trimers Ru₃O₁₂ of FSO in 2. In 3 and 4, the Ru₂O₉ units are connected by corners either directly (3) or through a slab of isolated RuO₆ octahedra (4) to form a bidimensional arrangement of RuO₆ octahedra. These four oxybromocarbonates belong to the family of compounds formulated [Ba₂Br_2−2x(CO₃)_x][Ba_n+1Ru_nO_3n+3] where n represents the thickness of the octahedral string in hexagonal perovskite slabs. These compounds are compared to the oxychloride series.     

Structure refinement, dielectric, pyroelectric and Raman characterizations of Ba1−xLax(1−y)/2Euxy/2Nax/2TiO3 solid solution

The perovskite-type oxides Ba_1−xLa_x(1−y)/2Eu_xy/2Na_x/2TiO₃ (0?x?0.5 and xy=0.04) were synthesized and characterized by X-ray diffraction as well as dielectric measurements and Raman spectroscopy. The crystal structure of these ceramics has been determined by the Rietveld refinement powder X-ray diffraction data at room temperature. These compounds crystallize at room temperature in tetragonal space group P4mm for 0?x?0.1 and in the cubic group for 0.2?x?0.5. The phase transition temperature T_C (or T_m) decreases as x content increases. The degree of diffuseness of the phase transition is more pronounced for higher x content, implying the existence of a composition-induced diffuse phase transition of the ceramics with x?0.1. The evolution of the Raman spectra was studied as a function of various compositions at room temperature. The polarization state was checked by pyroelectric measurements.     

Phase transitions in Ca3(BN2)2 and Sr3(BN2)2

α-Ca₃(BN₂)₂ crystallizes in the cubic system (space group: ) with one type of calcium ions disordered over of equivalent (8c) positions. An ordered low-temperature phase (β-Ca₃(BN₂)₂) was prepared and found to crystallize in the orthorhombic system (space group: Cmca) with lattice parameters: , , and . Structure refinements on the basis of X-ray powder data have revealed that orthorhombic β-Ca₃(BN₂)₂ corresponds to an ordered super-structure of cubic α-Ca₃(BN₂)₂. The space group Cmca assigned for β-Ca₃(BN₂)₂ is derived from by a group-subgroup relationship.DSC measurements and temperature-dependent in situ X-ray powder diffraction studies showed reversible phase transitions between β- and α-Ca₃(BN₂)₂ with transition temperatures between 215 and 240 °C.The structure Sr₃(BN₂)₂ was reported isotypic with α-Ca₃(BN₂)₂ () with one type of strontium ions being disordered over of equivalent (2c) positions. In addition, a primitive () structure has been reported for Sr₃(BN₂)₂. Phase stability studies on Sr₃(BN₂)₂ revealed a phase transition between a primitive and a body-centred lattice around 820 °C. The experiments showed that both previously published structures are correct and can be assigned as α-Sr₃(BN₂)₂ (, high-temperature phase), and β-Sr₃(BN₂)₂ (, low-temperature phase).A comparison of Ca₃(BN₂)₂ and Sr₃(BN₂)₂ phases reveals that the different types of cation disordering present in both of the cubic α-phases () have a directing influence on the formation of two distinct (orthorhombic and cubic) low-temperature phases.     

Three-dimensional framework of uranium-centered polyhedra with non-intersecting channels in the uranyl oxy-vanadates A2(UO2)3(VO4)2O (A=Li, Na)

The uranyl vanadates A₂(UO₂)₃(VO₄)₂O (A=Li, Na) have been synthesized by solid-state reaction and the structure of the Li compound was solved from single-crystal X-ray diffraction. The crystal structure is built from chains of edge-shared U(2)O₇ pentagonal bipyramids alternatively parallel to - and -axis and further connected together to form a three-dimensional (3-D) arrangement. The perpendicular chains are hung on both sides of a sheet parallel to (001), formed by U(1)O₆ square bipyramids connected by VO₄ tetrahedra, and derived from the autunite-type sheet. The resulting 3-D framework creates non-intersecting channels running down the - and -axis formed by empty face-shared oxygen octahedra, the Li⁺ ions are displaced from the center of the channels and occupy the middle of one edge of the common face. The peculiar position of the Li⁺ ion together with the full occupancy explain the low conductivity of Li₂(UO₂)₃(VO₄)₂O compared with that of Na(UO₂)₄(VO₄)₃ containing the same type of channels half occupied by Na⁺ ions in the octahedral sites.Crystallographic data for Li₂(UO₂)₃(VO₄)₂O: tetragonal, space group I41/amd, , , , Z=4, ρ_mes=5.32(2) g/cm³, ρ_cal=5.36(3) g/cm³, full-matrix least-squares refinement basis on F² yielded, R₁=0.032, wR₂=0.085 for 37 refined parameters with 364 independent reflections with I?2σ(I).     

Independent structural and valence state transitions in the cation-ordered double perovskites Ba2−xSrxTbIrO6

Synchrotron X-ray and neutron powder diffraction were used to investigate the formation, structure and bonding in the double perovskite Ba_2−xSr_xTbIrO₆ solid solutions. The results showed that these oxides all exhibit ordering of the Tb and Ir cations in a double perovskite-type structure. Three distinct structural types differing in symmetry and/or valence states were formed depending on the precise Ba:Sr ratio on the perovskite A site; x?0.3 cubic () with Tb⁴⁺ and Ir⁴⁺; 0.4?x?1.0 cubic () with Tb³⁺ and Ir⁵⁺ and x?1.2 monoclinic (P2₁/n) with Tb³⁺ and Ir⁵⁺. The transitions between these appear to be first order in nature.     

Synthesis and crystal structures of the layered uranyl tellurites A2[(UO2)3(TeO3)2O2] (A=K, Rb, Cs)

The reactions of UO₃ and TeO₃ with KCl, RbCl, or CsCl at 800 °C for 5 d yield single crystals of A₂[(UO₂)₃(TeO₃)₂O₂] (A=K (1), Rb (2), and Cs (3)). These compounds are isostructural with one another, and their structures consist of two-dimensional sheets arranged in a stair-like topology separated by alkali metal cations. These sheets are comprised of zigzagging uranium(VI) oxide chains bridged by corner-sharing trigonal pyramidal TeO₃²⁻ anions. The chains are composed of dimeric, edge-sharing, pentagonal bipyramidal UO₇ moieties joined by edge-sharing tetragonal bipyramidal UO₆ units. The lone-pair of electrons from the TeO₃ groups are oriented in opposite directions with respect to one another on each side of the sheets rendering each individual sheet non-polar. The alkali metal cations form contacts with nearby tellurite oxygen atoms as well as with oxygen atoms from the uranyl moieties. Crystallographic data (193 K, MoKα, ): 1, triclinic, space group , , , , α=101.852(1)°, β=102.974(1)°, γ=100.081(1)°, , Z=2, R(F)=2.70% for 98 parameters and 1697 reflections with I>2σ(I); 2, triclinic, space group , , , , α=105.590(2)°, β=101.760(2)°, γ=99.456(2)°, , Z=2, R(F)=2.36% for 98 parameters and 1817 reflections with I>2σ(I); 3, triclinic, space group , , , , α=109.301(1)°, β=100.573(1)°, γ=99.504(1)°, , Z=2, R(F)=2.61% for 98 parameters and 1965 reflections with I>2σ(I).     

From ordered antiferromagnet to spin glass: A new phase Mn4Ir7−xMnxGe6

A new ternary phase, Mn₄Ir_7−xMn_xGe₆ (0?x?1.3), was studied by X-ray and neutron powder diffraction and SQUID magnetometry. The crystal structure is cubic, of the U₄Re₇Si₆ type, space group , Z=2, with the lattice parameter at 295 K. Within the limited range of homogeneity small variations of the composition yield dramatic changes of the magnetic structure. For x=0 long-range antiferromagnetic order is formed below the transition temperature 228 K, with large magnetic moments on Mn, 4.11(9) μ_B at 10 K, in a magnetic unit cell , c_M=2a_C. In contrast, for x=1.3 spin glass behavior is observed below 90 K. The Mn atoms form an ideal cubic framework, on which geometric frustration of competing nearest and next nearest neighbor antiferromagnetic interactions is suggested to explain the composition sensitive magnetic properties. A TiNiSi-type phase, IrMnGe, is found in samples of 1:1:1 composition quenched from the melt.     

Correlation between structure and magnetic properties of Cd-substituted La0.7(Ca0.3−xCdx)MnO3 CMR manganites

Structural, electrical and magnetic properties of Cd-doped La_0.7(Ca_0.3−xCd_x)MnO₃ (0?x?0.3) manganites are presented. All compositions were indexed in the orthorhombic (Pnma) space group, except the Cd_0.3 sample, indexed as a combination of trigonal and orthorhombic (Pnma) space groups. Substitution of Ca by Cd has a strong influence on the magnetic and magnetoresistive properties of these compounds, continuously decreasing both the magnetic moment and the Curie temperature (from 3.5 μ_B and 270 K for the x=0 composition to 1.59 μ_B and 90 K for the fully doped x=0.3 one). Samples corresponding to x=0 and 0.1 show a semiconductor-metal transition at temperatures close to the Curie ones. The measured magnetoresistance change is about 49% at 270 K and 95% at 165 K for those samples, respectively. However, the x=0.2 and 0.3 compositions show insulating behaviour in the whole temperature range studied, with values of the magnetoresistance about 85% at 105 K and 74% at 90 K, respectively. The observed weakening of the double-exchange mechanism as the Cd doping level in these samples increases is discussed in terms of structural properties, cationic disorder and Mn³⁺/Mn⁴⁺content ratio.     

One-dimensional chains in uranyl tungstates: Syntheses and structures of A8[(UO2)4(WO4)4(WO5)2] (A=Rb, Cs) and Rb6[(UO2)2O(WO4)4]

Three new uranyl tungstates, A₈[(UO₂)₄(WO₄)₄(WO₅)₂] (A=Rb (1), Cs (2)), and Rb₆[(UO₂)₂O(WO₄)₄] (3), were prepared by high-temperature solid-state reactions and their structures were solved by direct methods on twinned crystals, refined to R₁=0.050, 0.042, and 0.052 for 1, 2, and 3, respectively. Compounds 1 and 2 are isostructural, monoclinic P2₁/n, (1): a=11.100(7), b=13.161(9), , β=90.033(13)°, , Z=8 and (2): , , , β=89.988(2)°, , Z=8. There are four symmetrically independent U⁶⁺ sites that form linear uranyl [O=U=O]²⁺ cations with rather distorted coordination in their equatorial planes. There are six W positions: W(1) and W(2) have square-pyramidal coordination (WO₅), whereas W(3), W(4), W(5), and W(6) are tetrahedrally coordinated. The structures are based upon a novel type of one-dimensional (1D) [(UO₂)₄(WO₄)₄(WO₅)₂]⁴⁻ chains, consisting of WU₄O₂₅ pentamers linked by WO₄ tetrahedra and WO₅ square pyramids. The chains run parallel to the a-axis and are arranged in modulated pseudo-2D-layers parallel to (0 1 0). The A⁺ cations are in the interlayer space between adjacent pseudo-layers and provide a 3D integrity of the structures. Compounds 1 and 2 are the first uranyl tungstates with 2/3 of W atoms in tetrahedral coordination. Such a high concentration of low-coordinated W⁶⁺ cations is probably responsible for the 1D character of the uranyl tungstate units. The compound 3 is triclinic, P1¯ a=10.188(2), b=13.110(2), , α=97.853(3), β=96.573(3), γ=103.894(3)°, , Z=4. There are four U positions in the structure with a typical coordination of a pentagonal bipyramid that contain uranyl ions, UO₂²⁺, as apical axes. Among eight W sites, the W(1), W(2), W(3), W(4), W(5), and W(6) atoms are tetrahedrally coordinated, whereas the W(7) and W(8) cations have distorted fivefold coordination. The structure contains chains of composition [(UO₂)₂O(WO₄)₄]⁶⁻ composed of UO₇ pentagonal bipyramids and W polyhedra. The chains involve dimers of UO₇ pentagonal bipyramids that share common O atoms. The dimers are linked into chains by sharing corners with WO₄ tetrahedra. The chains are parallel to [−101] and are arranged in layers that are parallel to (1 1 1). The Rb⁺ cations provide linkage of the chains into a 3D structure. The compound 1 has many structural and chemical similarities to its molybdate analog, Rb₆[(UO₂)₂O(MoO₄)₄]. However, the compounds are not isostructural. Due to the tendency of the W⁶⁺ cations to have higher-than-fourfold coordination, part of the W sites adopt distorted fivefold coordination, whereas all Mo atoms in the Mo compound are tetrahedrally coordinated. Distribution of the WO₅ configurations along the chain extension does not conform to its ‘typical’ periodicity. As a result, both the chain identity period and the unit-cell volume are doubled in comparison to the Mo analog, which leads to a new structure type.     

Three-dimensional molecular network, [{Cu(dps)2(SO4)}·3H2O·DMF]n, and its different third-order NLO performance (dps=4,4′-dipyridyl sulfide)

A new three-dimensional non-interpenetrating coordination polymer, [{Cu(dps)₂(SO₄)}·3H₂O·DMF]_n (1) (dps=4,4′-dipyridyl sulfide) was synthesized and structurally characterized. 1 crystallizes in triclinic system, space group P−1 with cell parameters of a=10.9412(1) Å, b=11.8999(1) Å, c=12.5057(1) Å, V=1400.7(3) Å³, Z=2, D_c=1.573 g cm⁻³, F(0 0 0)=686, μ=1.059 mm⁻¹. R₁=0.0436, wR₂=0.1148. In the polymeric architecture, serve as bridging coligands to connect highly puckered [Cu₂(dps)₂]_n frameworks resulting in a 3D motif containing channels for guest molecule inclusion. Quantum chemistry calculation shows that the third-order NLO properties of polymer 1 are controlled by groups and dps ligands, and metal ions have less influence on the third-order NLO properties.     

Crystal structure and phase transformations of calcium yttrium orthophosphate, Ca3Y(PO4)3

Crystal structure and phase transformations of calcium yttrium orthophosphate Ca₃Y(PO₄)₃ were investigated by X-ray powder diffraction, selected-area electron diffraction, transmission electron microscopy and optical microscopy. The high-temperature phase is isostructural with eulytite, cubic (space group ) with a=0.983320(5) nm, V=0.950790(8) nm³, Z=4 and D_x=3.45 Mg m⁻³. The crystal structure was refined with a split-atom model, in which the oxygen atoms are distributed over two partially occupied sites. Below the stable temperature range of eulytite, the crystal underwent a martensitic transformation, which is accompanied by the formation of platelike surface reliefs. The inverted crystal is triclinic (space group P1) with a=1.5726(1) nm, b=0.84267(9) nm, c=0.81244(8) nm, α=109.739(4)°, β=90.119(5)°, γ=89.908(7)°, V=1.0134(1) nm³, Z=4 and D_x=3.24 Mg m⁻³. The crystal grains were composed of pseudo-merohedral twins. The adjacent twin domains were related by the pseudo-symmetry mirror planes parallel to with the composition surface . When the eulytite was cooled relatively slowly from the stable temperature range, the decomposition reaction of Ca₃Y(PO₄)₃→β-Ca₃(PO₄)₂+YPO₄ occurred.     

Structure, energy band, and optical properties of NaLa(PO3)4 crystal

An alkali metal-rare earth phosphate crystal of NaLa(PO₃)₄ has been synthesized by high temperature solid-state reactions and structurally characterized by single crystal X-ray diffraction analysis, for the first time. It crystallizes in the monoclinic P2₁/n space group with lattice parameters: a=7.2655(3), b=13.1952(5), , β=90.382°(1), , Z=4. It is composed of LaO₈ polyhedra and [(PO₃)₄]⁴⁻ chains sharing oxygen atoms to form a three-dimensional framework, delimiting intersecting tunnels in which the sodium ions are located. The IR spectrum, absorption spectrum, and emission spectrum of the compound have been investigated. The absorption edge is located at 340 nm (3.60 eV). The calculated total and partial densities of states indicate that the top of valence bands is mainly built upon O-2p states which interact with P-3p states via σ (P-O) interactions, and the low conduction bands mostly originates from unoccupied La-5d states. The P-O bond is mostly covalent in character, and the ionic character of the Na-O bond is larger than that in the La-O bond.     

The Al stabilized phase Li3−3xAlxBO3

The structure of an Al³⁺ stabilized phase Li_3−3xAl_xBO₃ (x≈0.18) was determined by means of single crystal X-ray diffraction. This phase crystallizes in space group P6₁22 or P6₅22, with lattice constants , and Z=6. The unit cell consists of six layers of BO₃ groups with Li⁺ cations distributing statistically on five crystallographic sites, none of which is fully occupied. The Li sites are close to each other and a three-dimensional network results when Li sites only within 1.65 Å are connected. Significant ionic conductivity was observed for this phase.     

Hydrothermal synthesis, crystal structure, thermal behavior, ferromagnetic resonance and ferrimagmetic behavior of (C4H12N2)1.5[Fe3(HAsO4)1.02(HPO4)0.98(AsO4)0.88(PO4)0.12F5]

(C₄H₁₂N₂)_1.5[Fe₃(HAsO₄)_1.02(HPO₄)_0.98(AsO₄)_0.88(PO₄)_0.12F₅] has been synthesized by using mild hydrothermal conditions under autogeneous pressure. The crystal structure was solved from X-ray single crystal data. The compound crystallizes in the monoclinic P2₁/c space group. The unit cell parameters are a=8.270(7), b=22.028(3), , β=99.79(2)° with Z=4. The crystal structure is formed from [Fe₃(HAsO₄)_1.02(HPO₄)_0.98(AsO₄)_0.88(PO₄)_0.12F₅]³⁻ sheets with the piperazinium cations located in the interlayer space, compensating the anionic charge and establishing hydrogen bonds. The IR and Raman spectroscopies confirm the existence of both the arsenate/hydrogenarsenate and phosphate/hydrogenphosphate oxoanions and the presence of the piperazinium dication. The reflectance diffuse spectrum is in good agreement with the existence of iron(III) high spin cations in slightly distorted octahedral geometry. The values of the Dq and Racah parameters are Dq=1005, B=1020 and . The ESR spectroscopy shows the presence of ferromagnetic resonance. The g-value shifts from 1.99(1) in the 300-15 K range to 3.11(1) at lower temperatures. Magnetic measurements indicate the presence of a ferrimagnetic behavior with the existence of a weak hysteresis loop at 5 K.     

[Bi6O4.5(OH)3.5]2(NO3)11: a new anhydrous bismuth basic nitrate. Synthesis and structure determination from twinned crystals

The bismuth basic nitrate [Bi₆O_4.5(OH)_3.5]₂(NO₃)₁₁ crystallizes in the monoclinic space group P2₁ with , , , β=107.329(17)° and . Its structure has been determined from , twinned crystal X-ray data (16 781 reflections, 683 parameters, R=0.0703). It is built upon [Bi₆O_x(OH)_8−x]^(10−x)+, x=4 and x=5 hexanuclear complexes and nitrate groups. The polycationic entities are linked to the nitrate anions either by hydrogen bonds or through bismuth-oxygen coordination. Even at , the [Bi₆O₄(OH)₄]⁶⁺ and [Bi₆O₅(OH)₃]⁵⁺ polycations could not be observed as such, the crystal structure refinement only detecting an average [Bi₆O_4.5(OH)_3.5]^5.5+ polycation. To prove the presence of both hexanuclear complexes in the structure, we report the existence of a correlation between the bismuth-linked oxygen bond-valence parameters and the presence, or not, of hydroxyl groups. Moreover, the Raman spectrum of the new anhydrous bismuth basic nitrate is compared to those of [Bi₆O₅(OH)₃](NO₃)₅·3H₂O, [Bi₆O₄(OH)₄](NO₃)₆·4H₂O, and two yet uncharacterized bismuth nitrates.     

Synthesis and crystal structure of gallosilicate- and aluminogermanate tetrahydroborate sodalites Na8[GaSiO4]6(BH4)2 and Na8[AlGeO4]6(BH4)2

Tetrahydroborate enclathrated sodalites with gallosilicate and aluminogermanate host framework were synthesized under mild hydrothermal conditions and characterized by X-ray powder diffraction and IR spectroscopy. Crystal structures were refined in the space group P-43n from X-ray powder data using the Rietveld method. Na₈[GaSiO₄]₆(BH₄)₂: a=895.90(1) pm, V=0.71909(3)×10⁻⁶ nm³, R_P=0.074, R_B=0.022, Na₈[AlGeO₄]₆(BH₄)₂: a=905.89(2) pm, V=0.74340(6)×10⁻⁶ nm³, R_P=0.082, R_B=0.026. The tetrahedral framework T-atoms are completely ordered in each case and the boron atoms are located at the centre of the sodalite cages. The hydrogen atoms of the enclathrated anions were refined on x, x, x positions, restraining them to boron-hydrogen distances of 116.8 pm as found in NaBD₄.The IR-absorption spectra of the novel phases show the typical bands of the tetrahedral group as found in the spectrum of pure sodium boron hydride.The new sodalites are discussed as interesting -containing model compounds which could release pure hydrogen.