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We report a synthetic pathway by which amorphous Al(OH)3 is converted to γ-AlOOH through hydrothermal reaction in the presence of water at temperature T ​= ​473 ​K. X-ray pair distribution function measurements reveal that the initially amorphous Al(OH)3 possesses a locally γ-Al(OH)3-like structure, while nanocrystalline γ-AlOOH precipitates within 1 ​h of continuous hydrothermal exposure. Solid state nuclear magnetic resonance measurements show that resonant features associated with four- and five-member Al clusters persist through 20 ​min of hydrothermal treatment, and ultraviolet (UV) spectra mark the onset of UV-induced photoluminescent features characteristic to γ-AlOOH with 10 ​min of exposure, indicating a coexistence region of γ-Al(OH)3-like and γ-AlOOH-like amorphous species. Powder x-ray diffraction measurements of desiccated powders reveal that the conversion process takes place in distinct, power law-defined stages with initial γ-AlOOH nucleation occurring within the first 20 ​min, followed by a ~ 1 ​h period of rapid grain coarsening and the subsequent onset of Lifshitz-Slyozov-Wagner-like coalescence.

A three dimensional lithium hydronium sulfate LiSO4·H3O [1], [space group Pna21 a=8.7785(12) A, b=9.1297(12) A, c=5.2799(7) A, V=423.16(10) A3] was synthesized via solvothermal methods using 1,5-naphthalenedisulfonic acid (1,5-NSA) as the source of sulfate ions. The structure of [1], determined by single crystal X-ray diffraction techniques, consists of corner sharing LiO4 and SO4 tetrahedra, forming an anionic 3-D open framework that is charge balanced by hydronium ions positioned within channels running along [001] and forming strong H-bonding with the framework oxygen atoms. Compound [1] undergoes two reversible phase transitions, involving reorientation of SO42− ions at pressures of approximately 2.5 and 5 GPa at room temperature, as evident from characteristic discontinuous frequency drops in the ν1 mode of the Raman spectra. Additionally, compound [1] forms dense β-lithium sulfate at 300 °C, as evident from temperature dependent powder XRD and combined reversible TGA-DSC experiments.

Synchrotron X-ray single-crystal diffraction analyses revealed that as-synthesized and Na-exchanged RUB-29 (Cs 1− x , Na x ) 14 Li 24 [Si 72 Li 18 O 172 ]· y H 2 O ( x =0, 0.9) displays the lattice symmetry I 222. With increasing ion-exchange time, the Na cations preferentially replace Cs in the larger sites located at the intersections of the 10MR/10MR/8MR channels. The smaller Cs sites are then replaced. While Na cations are easily incorporated on the Cs sites, most of non-framework Li cations remain in the channel system. Relocation of Li cations onto new sites within the channels was observed only after 13 days of ion exchange. Using high-field (14.1 T) NMR spectroscopy, at least six separate 6 Li resonances could be resolved for the first time by solid-state 6 Li MAS NMR spectroscopy and assigned to Li in the framework and non-framework sites of the microporous lithosilicate materials. The fate of Li in both framework and extra-framework sites during exchange was also followed by 6 Li MAS NMR spectroscopy with an Na-exchanged RUB-29 powder sample.

Crystals of barium monogallate were obtained by growth from a stoichiometric melt at 1350°C. The hexagonal crystals belong to space group P 6 3 , a =18.6403(7) A and c =8.6801(2) A, V =2611.9(2) A 3 , Z =24, D calc. =5.20 g cm −3 . The structure was solved by Patterson techniques using a single crystal diffraction data set. Merohedral twinning of the crystal (twin element 2 [110] ) was accounted for in the refinement calculations (w R 2=0.056 for 4183 reflections). The main structural features of BaGa 2 O 4 are layers of six-membered rings of GaO 4 tetrahedra perpendicular to the c -axis. The stacking of the layers parallel to c results in a three-dimensional framework containing tunnels, where the barium cations are located. Within a single layer two different types of ditrigonal-shaped six-membered rings are distinguished on the basis of relative orientation of up (U) and down (D) pointing apices of adjacent tetrahedra: one-fourth of the rings have an UDUDUD topology, whereas the sequences of directedness of the remaining rings is UUUDDD. The structure is isotypic with KAlGeO 4 . It is the first member of this structure family containing exclusively trivalent tetrahedral ions of only one chemical species and divalent nonframework cations within the channels.

The structures of the two isostructural compounds Cs (TiAs)O 5 (CTA) and Cs(TiP)O 5 (CTP) were solved and refined by application of the Rietveld profile technique to high-resolution synchrotron X-ray and neutron powder data. The structures are cubic, space group F d 3 m with a = 10.23415(5) A (CTA) and a = 10.08733(2) A (CTP), and are characterized by an unusual framework consisting of randomly disordered TiO 6 octahedra and X O 4 ( X = As, P) tetrahedra with the Cs + cation occupying large cavities within this framework. The lack of long-range order between octahedra and tetrahedra simulates partially occupied octahedra shared by Ti and X with large displacement parameters for both cations and oxygens. The Ti, X -site can be resolved as a split-atom position where the tetrahedral metal is shifted from the center toward the edge formed by the octahedral oxygens. Split-oxygen positions were refined from a combination of X-ray and neutron data for CTA. The cubic structure is related to the orthorhombic KTiOPO 4 -type structure in that the latter can be derived from the former by ordering of the TiO 6 octahedra and PO 4 tetrahedra. Since different ordering schemes applied to the cubic CTA/CTP structure lead to other known ordered structures of the same stoichiometry such as K(Mg 1/3 Nb 2/3 )OPO 4 and γ-NaTiOPO 4 , cubic CTA/CTP can be viewed as the "mother of all ABOCO 4 -structures." The elucidation of the cubic structure allows us to propose a quantified "threatened structure model," which helps in the understanding of the mechanism of this phase transition.

Addition of triethylenetetramine (TETN) and tetramethylammonium (TMA+) to SnS2 and SnSe2 slurries followed by heating at 150°C under autogenous hydrothermal conditions results in novel thio and thio-oxide phases. These materials crystallize in time sequence as the added amines decompose. Initially 2-D frameworks with composition (Sn3X7)2-, X = S or Se are produced. In the case of the sulfides these are shown to transform to 2-D and 3-D oxy-sulfides frameworks which incorporate the decomposed template. The structures of two materials in this sequence have been determined from single crystal X-ray diffraction. The first, Sn3Se7 · C6N4H16CO, designated TETN-SnSe-1, crystallizes after 1 day of digestion in space group Pbca, with a = 23.553(6), b = 14.004(6), and c = 13.967(4) A. The structure contains SnSe5 coordination polyhedra which form Sn3Se4+4 semicubes; six such semicubes are linked via Se2 bridges to form apertures in the Sn3Se2-7 sheet in (010). Similar structures occur in the TETN-SnS and TMA-SnS systems. The second material, with a framework designated SnOS-SB3, is formed after 5 days of digestion in either the TMA-SnS or TETN-SnS systems and crystallizes in C2/c, with a = 35.62(1), b = 18.468(4), c = 21.858(6) A, and β = 115.36(1)°. The structure consists of tetrahedral clusters of composition [Sn10S20O4]8-, which are linked via single S bridges at three corners to form a 2-D framework of composition [Sn20S37O8]10-. This is one member of a theoretical structural family with composition [Sn10S20-n/2O4](8-n)-, where 0 ≤ n ≤ 4 and represents the number of connections between clusters.

A new framework with the composition [Sn4S9]2- has been synthesized hydrothermally in the presence of tetrapropylammonium (TPA) hydroxide. The structures of two compounds possessing this framework, Sn4S9[(C3H7)4N]2 (1) and Sn4S9[(C3H7)4N] · [(CH3)3NH] (2), have been solved using single-crystal X-ray diffraction data. Both crystallize in the space P 21/n (Z = 4) with unit cell parameters a = 15.497(5) A, b = 15.826(4) A, c = 18.594(5) A, β = 110.40(1)° for (1), and a = 14.832(4) A, b = 18.612(6) A, c = 15.039(6) A, β = 96.90(3)° for (2). These compounds are layered with organic cations accommodated between Sn-S sheets containing apertures composed of 16 SnS5 and SnS4 polyhedra. Both materials contain TPA+ cations, and (2) also incorporates trimethylammonium cation, a breakdown product of TPA.

Single-crystal and powder samples of a new calcium iron(II) titanate, CaFeTi 2 O 6 , have been synthesized at 12-15 GPa and 1200-1400°C, and studied by X-ray diffraction. This compound is a variant of the perovskite structure and crystallizes in the tetragonal space group P 4 2 / nmc , a = 7.5157(2) A, c = 7.5548(2) A, and Z = 4. Calcium and two iron atoms are ordered on three different A sites, with calcium in approximately 10-fold coordination, with one iron atom in tetrahedral coordination (Fe-O = 2.084(2)/A), and the other iron atom in square-planar coordination (Fe-O = 2.097(2) A). The system of octahedral tilts which this compound adopts has not been observed previously in a perovskite. The tilt system was described in a theoretical treatment of perovskites ( a + a + c - in the notation of A. M. Glazer ( Acta Crystallogr. Sect. B 28, 3384, 1972) and was (incorrectly) assigned to space group Pmmn.

We report the discovery of a new ternary oxynitride, Na3WO3N. Na3WO3N is synthesized by exposing a eutectic melt consisting of 1 2 Na2O : 1Na2WO4 to a flow of ammonia gas at 695°C. The compound crystallizes in the acentric space group Pmn21 with a = 7.2481(3) A, b = 6.2728(3) A, and c = 5.6493(2) A. The structure was determined from synchrotron X-ray powder diffraction data and refined using the Rietveld analysis on neutron powder diffraction data. It is isostructural to the low temperature form of Li3PO4 which can be derived from an ordered wurtzite structure-type with all the atoms having tetrahedral coordination. Alternatively, the structure can be described as being "salt-like" consisting of isolated (WO3N)-3 tetrahedral polyanions separated by Na+.

Single crystals and powdered samples of the bismuth(III) calcium oxide Ca 6 Bi 6 O 15 have been synthesized and studied using both X-ray and neutron diffractometry. The compound crystallizes in the space group P 1 with Z = 2. Cell parameters, obtained with the single-crystal X-ray diffractometer, were a = 10.101(3), b = 10.130(2), c = 10.466(2) A, and α = 116.86(1), β = 107.18(2), γ = 92.90(2)°. As with other materials in the series M -Bi-O ( M = Ca, Sr) studied thus far, at least some Bi is found in threefold coordination with oxygen; the remaining Bi are fourfold coordinated. The structure is related to that of Ca 4 Bi 6 O 13 , which has been studied using neutron powder diffraction. Both compounds are composed of layers containing alternating Bi- and Ca-rich segments. These layers stack to form Bi-rich slabs containing tunnels accommodating the Bi 6 s 2 lone pairs.

The structures of CaYAlO 4 , CaNdAlO 4 , and SrLaAlO 4 have been refined using single-crystal X-ray diffraction data. These compounds possess the full symmetry of the K 2 NiF 4 structure type, I4 mmm , with lattice parameters a = 3.6451(1) and c = 11.8743(6)A for CaYAlO 4 , a = 3.6847(3) and c = 12.124(2)A for CaNdAlO 4 , and a = 3.7564(1) and c = 12.6357(5)A for SrLaAlO 4 . Inspection of the interatomic distances reveals stretching of the AlO bond, from an average of 1.878 to 1.901 to 1.935 A, as smaller cations (CaY) are replaced by larger cations (CaNd) and (SrLa) in the MM′ sites between the two dimensional aluminate sheets. The dielectric constants (κ′) and dielectric loss values of CaYAlO 4 , CaNdAlO 4 , and SrLaAlO 4 were measured at 1 MHz using a two-terminal method with empirically determined edge corrections. The results are CaYAlO 4 κ′ a = 21.44 ± .02 tan δ a = 0.0008 κ′ c = 16.12 ± .04 tan δ c = 0.0008 CaNdAlO 4 κ′ a = 19.65 ± .1 tan δ a = 0.0002 κ′ c = 17.65 ± .1 tan δ c = 0.0004 SrLaAlO 4 κ′ a = 16.81 ± .1 tan δ a = 0.0006 κ′ c = 20.02 ± .1 tan δ c = 0.0008. The deviations of measured dielectric polarizabilities, as determined from the Clausius-Mosotti equation and those calculated from the sum of oxide polarizabilities according to α D ( MM ′AlO 4 ) = α D ( M O) + 0.5 α D ( M ′ 2 O 3 ) + 0.5 α D (Al 2 O 3 ), are + 1.7% for CaYAlO 4 , −2.0% for CaNdAlO 4 , and −5.9% for SrLaAlO 4 . The deviations from additivity are believed to result from K 2 NiF 4 structural constraints leading to “rattling” M and M ′ ions in CaYAlO 4 and “compressed” M and M ′ ions in CaNdAlO 4 and SrLaAlO 4 .

The structure of the distorted anti-perovskite nitride Ca 3 AsN has been studied both by neutron powder diffraction at 305 and 15 K and by X-ray powder diffraction at room temperature. Ca 3 AsN is distorted to an orthorhombic cell with a and b ‡ a′ and c ∼ 2 a′ , where a′ is the lattice constant of the ideal undistorted cubic anti-perovskite. The distortion is produced by tilting of octahedra of Ca 6 N and results in six short and six long bond distances of the twelvefold coordinated As atom by Ca atoms.

The bismuth(III) strontium oxide Sr 2 Bi 2 O 5 has been synthesized in the low-temperature form, and studied using both single-crystal X-ray and powder neutron diffractometry. All bismuth atoms are in an unusual threefold coordination with oxygen. The compound crystallizes in the orthorhombic space group Pnma with Z = 4 and X-ray cell parameters a = 14.261(3), b = 6.160(2), c = 7.642(3)A. A superlattice, visible in long exposure precession photographs, exists along c (2 × 3.8A). This is due to the ordering of oxygen and vacancies along the c -axial direction, and to resulting displacements of the Bi atoms along c . The structure consists of an ordered intergrowth, along the a -axial direction, of slabs of inverse NiAs-type, with composition Sr 2 O 4 and strings of Bi O Bi···□···Bi O Bi···, where □ represents an oxygen vacancy.

Powdered samples of {beta}-MoO{sub 3} have been produced by the gentle heat treatment of freeze-dried molybdic acid at 350{degree}C for 1 hr. The samples, yellow-green in appearance, contained varying amounts of the thermodynamically stable {alpha}-MoO{sub 3}, depending upon the time and temperature of heat treatment. Neutron diffraction data were collected at 300 K. all peaks, not attributable to {alpha}-MoO{sub 3}, were indexed on the basis of a monoclinic cell, P2{sub 1}/c, {alpha} = 7.1228(7), b = 5.3660(6), c = 5.5665(6), {beta} = 92.01(1){degree}, V = 212.62(6){angstrom}{sup 3}. The structure, which is related to ReO{sub 3}, contains two crystallographically independent octahedra. Both show evidence of disorder at the Mo and O sites. Two distinct orientations of a short mo-O distance, suggestive of the type of molybdenyl bond observed in both the {alpha} and {beta}{prime}-forms, are primarily responsible for the observed disordering.

The structure of an orthorhombic variant of Tl 2 Ba 2 CuO 6 ( Z = 4), with a superconducting onset at 90 K, has been studied using neutron powder diffractometry at 12 K ( a = 5.4834(3), b = 5.4586(3), c = 23.198(1) A), 60 K ( a = 5.4834(3), b = 5.4585(3), c = 23.199(1)A), and 293 K ( a = 5.4967(3), b = 5.4651(3), c = 23.246(1) A). The distortion from I4 mmm symmetry, reported in single-crystal X-ray investigations, to Abma is manifested in the TIO layer. At the temperatures studied, the coordination of TI to oxygen is (2 + 1 + 2) square pyramidal rather than octahedral. At lower temperatures, distortion decreases but does not disappear. Despite the orthorhombic symmetry the CuO 2 -layers remain flat.

Substitution of Ca2+ for Y3+ in YBa2Cu3O6 converts this tetragonal semiconductor into a tetragonal superconductor with aTc of 50 K. Furthermore, the structure of (Y0.8Ca0.2)Ba2Cu3O6, determined by neutron powder diffraction, is fully consistent with partial oxidation of the Cu(2) O sheets, whereas the linear O Cu(1) O units do not undergo oxidation. Observation of a limited solid solubility for Ca2+ in this structure is attributed to a maximum allowed oxidation state for Cu(2). This implies that in the superconductor YBa2Cu3O7 the Cu O chains are responsible for theTc of 90 K, whereas the Cu O sheets alone produce superconductivity at 50 K in YBa2Cu3O6.5.

Crystals of the 110 K superconductor TlBa2Ca2Cu3O9 have been grown and the structure refined from single-crystal X-ray diffraction data: a = 3.853(1), c = 15.913(4)A, space group P4 mmm , R = 0.055, R w = 0.057 . The structure contains triple copper-oxygen sheets separated by Ca ions which show ∼5% Tl substitution. These units alternate with single TlO layers. The existence of correlated atomic displacements within the thallium-oxygen sheets is again suggested by a disordered TlO arrangement in the average structure. The triple CuO sheets in TlBa2Ca2Cu3O9 are stacked directly above each other, whereas in Tl2Ba2Ca2Cu3O10, which contains double TlO sheets, alternate units are shifted by (a 1 + a 2 ) 2 .

Replacing Y( III ) by Ca( II ) in (Y 1− x Ca x )Ba 2 Cu 3 O 6 induces superconductivity. A solid-solution limit exists, as is evidenced by the lack of variation in unit cell parameters for values of x > 0.3. At low nominal doping levels ( x 2 Cu 3 O 6 and BaCuO 2 . At higher nominal doping levels the Ca content of the 123-type phase becomes constant ( x ∼ 0.30). Structural refinements using data collected by X-ray and neutron powder diffractometry are consistent with Ca-doping causing oxidation only of Cu in the sheet, leaving the copper in the so-called chain site as Cu(I). Many of the structural changes occurring in this system upon oxidation, such as a flattening of the CuO 2 sheets, a contraction of the in-plane CuO distance, and a decrease in the CuCu distance between planes, also occur in the structurally related superconducting system, Pb 2 Sr 2 (Y 1− x Ca x )Cu 3 O 8 .

The critical temperature for superconductivity in the (Ba, K)BiO 3 system has been increased to 34 K. With each such increase of T c in a system containing no copper it becomes increasingly likely that the mechanisms for superconductivity in the Bi-based and the Cu-based oxide superconductors are very closely related to each other. Since the (Ba, K)BiO 3 superconductors possess the cubic perovskite structure, the mechanism for high T c would then not related directly to the two-dimensional character of the copper oxide superconductors or to the magnetism in such systems.