O4 Tetrahedra Research Articles

Modulated structure of nepheline

The incommensurately modulated structure of a natural nepheline of composition K(0.54)Na(3.24)Ca(0.03)Al(3.84)Si(4.16)O(16) has been determined in superspace. The compound crystallizes in the trigonal centered superspace group X3(00γ)0 with γ = 0.2048 (10), X = (0, 0, 0, 0), (1/3, 2/3, 0, 2/3), (2/3, 1/3, 0, 1/3), a = 17.2889 (8) and c = 8.3622 (10) Å. The structure is characterized by a framework of corner-connected (Al,Si)O(4) tetrahedra. The additional cations are incorporated in two different types of channels of the framework. All atoms in the structure are displacively modulated with amplitudes below 0.1 Å. The modulation can be well described taking into account harmonics of first order only. Atomic positions in the smaller channels of the framework are fully occupied by Na(+). Cationic positions in the larger channel are occupationally modulated, yet the variation of electron density as a function of the internal coordinate t is very small and indicates that the incorporation of different types of cations (K(+), Na(+), Ca(2+)) and vacancies is realised in a highly disordered way. Average T-O distances indicate a nearly complete Al/Si ordering in the tetrahedral framework. A large part of the O atoms are approximated by split-atom positions, which are additionally affected by occupational modulation resulting in a high degree of disorder in the modulated structure. Occupational probabilities for the split-atom positions are complementary. Occupational modulations of the cations in the larger channels and the O atoms of the tetrahedral framework are coupled and correlations between occupational and displacive modulations exist.

Room temperature synthesis of Ti-SBA-15 from silatrane and titanium-glycolate and its catalytic performance towards styrene epoxidation

A novel room temperature sol–gel synthesis of Ti-SBA-15 is described using moisture stable silatrane and titanium glycolate precursors, and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer (EO20PO70EO20) as the structure directing agent. Catalyst performance was optimized by systematically investigating the influence of acidity, reaction time and temperature, and titanium loading. Small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) showed well-ordered 2D mesoporous hexagonal structures, while N2 adsorption/desorption measurements yielded high surface areas (up to 670 m2/g), with large pore diameters (5.79 nm) and volumes (0.83 cm3/g). Diffuse reflectance UV–visible spectroscopy (DRUV) was found that tetravalent titanium as Ti4+O4 tetrahedra were incorporated in the framework through displacement of Si4+O4 after calcination (550°C/6 h) to loadings of 7 mol% Ti without perturbation of the ordered mesoporous structure, or decoration by extra-framework anatase containing Ti4+O6 octahedra. The catalytic activity and selectivity of styrene epoxidation using hydrogen peroxide (H2O2) showed that the conversion of styrene increases significantly at higher titanium contents. The only products of this reaction were styrene oxide and benzaldehyde, with selectivity of 34.2 and 65.8%, respectively, at a styrene conversion of 25.8% over the 7 mol% Ti-SBA-15 catalyst. Beyond this titanium loading, anatase is deposited on the framework and catalytic activity degrades. The performance of the new catalyst is also shown to be superior to conventional materials produced by incipient wetness impregnation where Ti resides on the surface of SBA-15, giving a styrene conversion of 11.9% under identical reaction conditions.

Ardennite, tiragalloite and medaite: structural control of (As5+,V5+,Si4+)O4 tetrahedra in silicates

AbstractSeveral silicate-minerals, such as ardennite – Mn2+4MgAl5[Si5(As5+,V5+)O22](OH)6, Z = 2, tiragalloite – Mn2+4[Si3As5+O12(OH)], Z = 4 and medaite – Mn2+6[Si5(V5+,As5+)O18(OH)], Z = 4 possess (V5+,As5+,P5+)O4 tetrahedra. Using electron-microprobe analysis (EMPA) and single-crystal X-ray diffraction methods, the crystal chemistry of ardennite from Salam-Château, Belgium and the Vernetto mine, Italy, tiragalloite from the Gambatesa mine, Italy, and medaite from the Molinello mine, Italy and the Fianel mine, Switzerland, were studied. Structure refinements converged to R1 values of 2.10–5.67%. According to chemical analysis, the Σ(As+V+P) content increases with decreasing Si content. Thus, Si replaces pentavalent cations in tetrahedral coordination. The (As5+,V5+,P5+,Si4+)O4 tetrahedra are categorized by their connections to SiO4 tetrahedra. The (As5+,V5+,P5+,Si4+)O4 tetrahedron of ardennite is isolated, and those of tiragalloite and medaite terminate a tetrahedral chain. The <T–O> of the isolated (As5+,V5+,P5+,Si4+)O4 tetrahedron shows a positive correlation with the mean ionic radius. For (As5+,V5+,P5+,Si4+)O4 tetrahedra with one T–O–T link, <T–O> and mean ionic radius are also correlated. In addition, the longest bridging T–O bond occurs between (As,V,P,Si)O4 and the adjacent SiO4 tetrahedron. The bridging O atom is over-bonded to satisfy the charge requirement of Σ(As+V+Si).

Low Thermal Expansion RBa(Co,M)4O7 Cathode Materials Based on Tetrahedral-Site Cobalt Ions for Solid Oxide Fuel Cells

RBa(Co,M)4O7 (R = Y, Ca, In and M = Zn, Fe, Al) oxides with a hexagonal structure and corner-shared (Co,M)O4 tetrahedra have been synthesized and investigated as cathode materials for solid oxide fuel cells (SOFC). Among the various compositions investigated, YBaCo4−xZnxO7 (1 ≤ x ≤ 2) shows long-term stability at high temperatures. Thermal expansion coefficient (TEC) values of the RBa(Co,M)4O7 specimens were determined to be 6 × 10−6 to 13 × 10−6 oC−1 in the range of 80−900 °C, which provides good thermal expansion compatibility with the standard SOFC electrolyte materials. The low TEC is attributed to the absence of spin state transitions of tetrahedral-site Co2+/3+ ions and relatively small amount of oxygen loss with increasing temperature. The YBaCo3ZnO7 + GDC composite cathodes exhibit low polarization resistance and good fuel cell performance comparable to that of well-studied Co-based perovskite cathodes, but with the critical advantage of an ideal matching of the TEC value with those of standard el...

First Mixed Alkaline Uranyl Molybdates: Synthesis and Crystal Structures of CsNa3[(UO2)4O4(Mo2O8)] and Cs2Na8[(UO2)8O8(Mo5O20)

AbstractTwo new mixed alkaline uranyl molybdates CsNa3[(UO2)4O4Mo2O8] (1) and Cs2Na8[(UO2)8O8(Mo5O20)] (2) have been obtained by high‐temperature solid state reactions. Their crystal structures have been solved by direct methods: Compound 1: triclinic, P$\bar{1}$, a = 6.46(1), b = 6.90(1), c = 11.381(2) Å, α = 84.3(1), β = 91.91(1), γ = 80.23(1)°, V = 488.6(2) Å3, R1 = 0.06 for 2865 unique reflections with |Fo| ≥ 4σF; Compound 2: orthorhombic, Ibam, a = 6.8460(2), b = 23.3855(7), c = 12.3373(3) Å, V = 1975.2(1) Å3, R1 = 0.049 for 2120 unique reflections with |Fo| ≥ 4σF. The structure of 1 contains complex sheets of UrO5 pentagonal bipyramids and molybdenum polyhedra. The sheets have [(UO2)2O2(MoO5)] composition. Natrium and cesium atoms are located in the interlayer space. Cesium atoms are situated between the molybdenum clusters, whereas natrium atoms are segregated between the uranyl complexes. The large Cs+ ions are localized between the Mo2O9 groups and force the molybdenum polyhedra to rotate relative to the [(UO2)2O2(MoO5)] sheets. Such rotation is impossible for U6+ polyhedra due to their rigid edge‐sharing complexes. The distance between the U6+ polyhedra vertices of neighboring layers is 3.8 Å, that allows the Na+ ion to be positioned between the uranyl groups. The crystal structure of 2 is based upon a framework consisting of [(UO2)2O2(MoO5)] sheets parallel to (010). The sheets are linked into a 3‐D framework by sharing vertices with the Mo(2)O4 tetrahedra, located between the sheets. Each MoO4 tetrahedron shares two of its corners with two MoO6 octahedra in the sheet above, and the other two with MoO6 octahedra of the sheet below. Thus four MoO6 octahedra and one MoO4 tetrahedron form chains of composition Mo5O18. The resulting framework has a system of channels occupied by the Cs+ and Na+ ions.

Orientational ordering of three SiO4 tetrahedra in α´L-Ca1.5Sr0.5SiO4 that satisfies bond-valence requirements and avoids O-O repulsion

The crystal structure of α´L-Ca1.55(4)Sr0.45(4)SiO4 was analyzed by single-crystal X-ray diffraction. Refinement with isotropic temperature factors yielded R = 5.4%. The occupancies of the M(11), M(12), M(13), M(21), M(22), and M(23) sites by Sr are 0.40(3), 0.37(3), 0.42(3), 0.11(3), 0.04(2), and 0, respectively. The structure contains SiO4 tetrahedra in three different orientations. The orientational ordering of the Si(n)O4 (n = 1-3) tetrahedra accommodates the M(1n)-O (n = 1-3) bond-valence unbalances caused by the ionic radii mismatch and also avoids increasing the O-O electric repulsions between adjacent Si(n)O4 tetrahedra.

The struvite‐type compounds M [Mg(H2O)6](X O4), where M = Rb, Tl and X = P, As

AbstractPhases with composition M [Mg(H2O)6](X O4), where M = Rb, Tl and X = P, As, were obtained by means of the gelatine‐gel diffusion technique from Mg‐EDTA and corresponding metal phosphate/arsenate solutions at pH > 9. The crystal structures were determined from single crystal X‐ray diffractometer data sets. All compounds crystallize isotypically with two formula units in the orthorhombic struvite [NH4[Mg(H2O)6](PO4)] structure type in space group Pmn 21 and with lattice parameters of a ≈ 6.88, b ≈ 6.16, c ≈ 11.34 Å. The structures consist of slightly distorted [Mg(OH2)6] octahedra (m symmetry), X O4 tetrahedra (m symmetry) and [M O10] polyhedra (m symmetry) as single building units, held together by an intricate hydrogen bonding network. The structure can also be described as made up of closed packed pseudo ‐hexagonal layers of [Mg(OH2)6] units stacked along [010] with the X O4 tetrahedra and the M atoms in the voids of this arrangement. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A New Magnetically Ordered Polymorph of CuMoO4: Synthesis and Characterization of ε-CuMoO4

A new polymorph of CuMoO4, e-CuMoO4, has been synthesized and characterized. The material exhibits a three-dimensional structure with tetramers of edge-shared Cu2+O5 square pyramids that link to the Mo6+O4 tetrahedra. Magnetic susceptibility measurements indicate that the material orders magnetically, with a ferromagnetic component below 10 K.

The effect of oxygen vacancies and aluminium substitution on the high-pressure properties of brownmillerite-structured Ca2Fe2−x Al x O5

The structural evolution with pressure and the equations of state of three members of the brownmillerite solid solution, Ca2(Fe2−x Al x )O5, have been determined by single-crystal X-ray diffraction up to a maximum pressure of 9.73 GPa. The compositions of the samples were x = 0.00 and x = 0.37 (with Pnma symmetry) and x = 0.55 (with I2mb symmetry). No phase transitions were observed in the experiments. The equation of state parameters determined from the pressure-volume data are K 0T = 128.0 (7) GPa, K′0 = 5.8 (3) for the sample with x = 0.00, K 0T = 131 (2) GPa, K′0 = 5.5 (4) for x = 0.37, and K 0T = 137.5 (6) GPa, K′0 = 4 for x = 0.55. The bulk modulus therefore increases with Al content, being 11% higher in the x = 0.55 sample than in the Al-free sample. The unit-cell compression is anisotropic, with the c-axis being stiffer than a or b, and the anisotropy increases with increasing Al content of the structure. The structural response to pressure of all samples is similar. The (Al,Fe)O4 tetrahedra and the (Al,Fe)O6 octahedra undergo approximately isotropic compression. There is an increase in the twists of the chains of corner-sharing (Al,Fe)O4 tetrahedra, and an increase in the tilts of the (Al,Fe)O6 octahedra, because these framework polyhedra are stiffer than the Ca–O bonds to the extra-framework Ca site. The alignment of the two shortest Ca–O bonds sub-parallel to [001] accounts for the relative stiffness of the c-axis and thus the elastic anisotropy.

Synthesis and Crystal Structure of Tl2[(S0.6Se0.4)O4]Te(OH)6

The crystal structure of the thallium sulfate selenate tellurate Tl2[(S0.6Se0.4)O4]Te(OH)6 was determined with single-crystal X-ray diffraction data. The title compound crystallizes in the monoclinic system with the P21/c space group. The unit-cell dimensions at 298 K are a = 12.3580(10)Å, b = 7.2310(10)Å, c = 11.9860(10)Å, β = 111.090(10)°, V = 999.33(19)Å3, Dx = 5.029 g/cm3, and Z = 4. The R value is 0.047 for 1799 reflections. The anions are disposed in a number of sheets of pure (S,Se)O4 tetrahedra, alterning with sheets of pure Te(OH)6 octahedra. All of those planes are intercalated in a bidimensional arrangement by Tl+ cations.

The Oxide Ba6Ga2Co11O26: A New Close-Packed Stacking Derived from the Hexagonal Perovskite

Single crystals of a new compound, Ba6Ga2Co11O26, have been grown by a self-flux method. The structure determined by single-crystal X-ray diffraction and transmission electron microscopy (TEM) techniques shows a complex intergrowth between an hexagonal perovskite block, corresponding to the 5H term, and a complex block [Ba(Ga,Co)8O11]. It crystallizes in the P3̄m1 trigonal space group with the following unit-cell parameters: a = 5.652(2) Å, b = 5.652(2) Å, c = 18.828(8) Å, and γ = 120°. The structural analogy with two structural types, namely rocksalt and nolanite, allows a description of the nature of the [Ba(Ga,Co)8O11] block: one central [111]RS Co4O8 slab, related to a CdI2-type slice, is sandwiched between two Ba(Ga,Co)2O3 nolanite-type slabs containing (Co/Ga)O4 tetrahedra and (Co/Ga)O6 octahedra. This compound can be thus viewed as the n = 5 member of the large series [Ba(Ga,Co)8O11][BaCoO3]n, opening the route toward the discovery of new cobaltites.

A novel double-function porous material: zeolite-activated carbon extrudates from elutrilithe

Zeolite-activated carbon (ZEOAC) extrudates were synthesized from natural elutrilithe through a two-step process consisting of the chemical activation of elutrilithe with K2CO3 at 800°C followed the hydrothermal transformation in NaOH solution. During the chemical activation, carbon in elutrilithe was activated, and the kaliophilite crystalline phase with framework structure of linked (Si, Al)O4 tetrahedra was formed simultaneously, which was then converted into zeolite A in alkaline medium. The as-synthesized samples were characterized by thermal gravimetric and differential thermal analyses (TG/DTA), N2 adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) and adsorptive capacities for water and hexane. The results show that this new material ZEOAC possesses the typical characteristics of zeolite and activated carbon, micro- and mesoporous structure, hydrophilic and hydrophobic properties.

Forms and origin of structure modulation in lazurites

The crystal structure of lazurite, ideally Na6Ca2[Al6Si6O24](SO4,S)2, has a flexible framework formed with four- and six-membered rings of the (Al,Si)O4 tetrahedra shared by vertices. The framework cavities are occupied with Na,Ca cations and S-containing anionic groups. Six modulated lazurite polymorphs have been studied using X-ray diffraction techniques. General and special features of the structure modulation of lazurites are discussed for several different structures. A mechanism of commensurate modulation is revealed using the triclinic structure as an example. The 3D incommensurate modulation of the cubic framework is shown. The commensurate 1D-modulation of the triclinic structure is compared with the incommensurate 1D-modulation of the monoclinic structure. The S-containing groups are believed to play an important role in the formation of the structure modulations.

Effect of Aluminum on the Formation of Silver Metal Quantum Dots in Sol–Gel Derived Alumino-Silicate Glass Film

The effect of aluminum incorporation on silver metal quantum dots formation in the alumino-silicate glass film processed by sol-gel process was investigated. The sol-gel derived glass was coated onto the silica glass plate by spin coating with the mixture solution of tetraethyl orthosilicate (TEOS), C2H5OH, H2O, AgNO3, Al(NO3)3. 39H2O, and HNO3 with the molar ratios of Ag/Si = 0.12 and Al/Si varying from 0 to 0.12. The formation of the silver metal quantum dots was confirmed by the measurements of the UV/VIS optical spectra, the X-ray diffraction patterns, and the transmission electron microscope images. While the radius of silver metal quantum dots increased with the increase of aluminum concentration, the concentration of the silver metal quantum dots decreased. The formation of the silver metal quantum dots was found strongly suppressed by incorporation of aluminum ions in the glass. The change in the glass structure due to the aluminum incorporation was investigated by the analysis of the Raman spectra. The silver ions in the glass contributed to form stable (Al:Ag)O4 tetrahedra by pairing with aluminum ions and thus clustering of silver metal quantum dots was hindered.

A second polymorph of [H3N(CH2)3NH3][V4O10

The title compound, propane-1,3-diammonium tetravanadate, (C3H12N2)[V4O10], represents a second polymorph of composition beta-[H3N(CH2)3NH3][V4O(10)]. It differs from the alpha polymorph [Riou & Ferey (1995). J. Solid State Chem. 120, 137-145] in the conformation of the propane-1,3-diammonium dication which, in the present example, lies on a twofold axis and adopts a syn-syn rather than a syn-anti conformation. The twofold symmetry of this conformation thus co-operates with the vanadium oxide framework to result in a higher symmetry for the resultant crystal, viz. C2/c versus P2(1)/n. The overall unit-cell parameters for the two polymorphs are similar, and the inorganic layer within each is topologically identical, comprising edge-sharing V(IV)O5 square pyramids linked together via corner-sharing with V(V)O4 tetrahedra. A key difference between the two polymorphs is a ;head-to-head' versus ;head-to-tail' stacking of the vanadyl groups in adjacent layers.

Synthesis and crystal structure of Li3.17(P0.69Ge0.24Mo0.07)O4

The crystal structure of Li3.17(P0.69Ge0.24Mo0.07)O4, which was synthesized by the flux method under the action of an electric field with a potential difference of 0.8 V, was studied by X-ray diffraction on a Nonius Kappa CCD diffractometer (MoKα radiation, λ = 0.71073 A, R = 0.0137). The crystal structure is based on a tetrahedral framework typical of γ-Li3PO4. The framework of the new compound is formed by (P,Ge,Mo)O4 and LiO4 tetrahedra. The positions of additional Li atoms in the structure of Li3.17(P0.69Ge0.24Mo0.07)O4 are found to be different from those in the structure of Li3.31(P0.69Ge0.31)O4, which is synthesized in the absence of an electric field and also belongs to the γ-Li3PO4 structure type.

The crystal structure of perhamite

AbstractThe crystal structure of perhamite, (Ca,Sr)3Al7.7Si3P4O23.5(OH)14.1 8H2O, from the Emmons mine, Maine, USA, has been determined using single crystal X-ray data. The average structure has trigonal symmetry, Pml, with cell parameters a=7.021(1) Å and c = 20.218(1) Å. It was refined to R1 = 0.044 for 618 observed reflections. The structure comprises ordered blocks of crandallite-type structure, centred at z = 0, intergrown parallel to (001) with disordered aluminosilicate structure blocks centred at z = 1/2 to form a microporous structure containing large channels along [100]. These channels are bounded by 8-member rings of 6 tetrahedra (2 SiO4, 2 A1O4 and 2 PO4) and 2 A1O6 octahedra. Calcium atoms and water molecules are distributed in the [100] channels. A model was developed for the local ordering of silicon into the fractionally occupied sites in the (001) layer at z = 1/2 and this model was refined in space group P321 to R1 = 0.041 for 933 observed reflections. The dominant contributors to the local order are Si3O9 rings of corner-shared tetrahedra, together with Si2O7 pairs of tetrahedra. These units corner-link to (Al,Si)O4 tetrahedra above and below the plane at z = 1/2 to form 4-member rings, which in turn corner-share to PO4 tetrahedra in the crandallite blocks to give the 8-member rings. The analysis suggests that 5-coordinated Si may also be present in the (001) plane at z = 1/2.

Effect of Ball-Milling on Porous Structure of Ca-Substituted Leucite Porous Body with Low Thermal Expansion Coefficient

The ball-milling for amorphous calcined powder in a PMMA solution, prepared by heating a mixture of nitrates, γ-Al2O3, and amorphous SiO2 powders were effective for the fabrication of Ca-substituted leucite porous bodies with almost homogeneous pore-size distributions. Especially, when the amorphous powder calcined at 1073 K was ball-milled for 48 h, the pore size decreased to 0.159 μm and porosity increased in the porous body fabricated using the amorphous calcined powder. The FT-IR spectroscopy revealed that the amorphous calcined powder is composed of fine particles having a network of (Si, Al)O4 tetrahedra similar to the aluminosilicate framework of the leucite compounds. The fabricated porous body showed a low linear thermal expansion coefficient of 1.405×10-6/K in the temperature range of 298 to 1273 K.

Design of a "green" one-step catalytic production of epsilon-caprolactam (precursor of nylon-6).

The ever-increasing industrial demand for nylon-6 (polycaprolactam) necessitates the development of environmentally benign methods of producing its precursor, epsilon-caprolactam, from cyclohexanone. It is currently manufactured in two popular double-step processes, each of which uses highly aggressive reagents, and each generates substantial quantities of largely unwanted ammonium sulfate as by-product. Here we describe a viable laboratory-scale, single-step, solvent-free process of producing epsilon-caprolactam using a family of designed bifunctional, heterogeneous, nanoporous catalysts containing isolated acidic and redox sites, which smoothly convert cyclohexanone to epsilon-caprolactam with selectivities in the range 65-78% in air and ammonia at 80 degrees C. The catalysts are microporous (pore diameter 7.3 A) aluminophosphates in which small fractions of the Al(III)O4(5-) and P(V)O4(3-) tetrahedra constituting the 4-connected open framework are replaced by Co(III)PO4(5-) and Si(IV)O4(4-) tetrahedra, which become the loci of the redox and acidic centers, respectively. The catalysts may be further optimized, and already may be so designed as to generate selectivities of approximately 80% for the intermediate oxime, formed from NH2OH, which is produced in situ within the pore system. The advantages of such designed heterogeneous catalysts, and their application to a range of other chemical conversions, are also adumbrated.

Two new cobalt–zinc orthophosphate monohydrates: hydrothermal synthesis, crystal structures and thermal investigation

Two new cobalt zinc orthophosphate hydrates with similar chemical formula, (CoxZn(1-x))3(PO4)2.H2O, but different composition and structure, have been prepared by systematic hydrothermal synthesis from the system nCo(CH3COO)2 : (1 -n)Zn(CH(3)COO)2 : 3.5H3PO4 : 2.1(CH3)2NH(CH2)3NH2:144H2O (0 </= n </= 1). The material Co(2.59)Zn(0.41)(PO4)2.H2O 1 has a three-dimensional structure that can be considered to be built from layers of edge-sharing CoO(6) octahedra joined by edge-sharing (Co/Zn)O(5) trigonal bipyramids, which also share edges with PO(4) tetrahedra. Compound 2, Co(0.72)Zn(2.28)(PO(4))(2).H(2)O, is isostructural with a known phase of Zn(3)(PO(4))(2).H(2)O: its structure contains corner-sharing (Zn/Co)O6 octahedra, (Zn/Co)O4 tetrahedra and PO4 tetrahedra, forming channels into which the coordinated water molecules project. Magnetic susceptibility measurements for 1 and 2 are consistent with the chemical compositions determined by the single-crystal X-ray analyses and with the presence of Co2+. The range for possible Co/Zn substitution in 1 and 2(assessed by EDX analysis) is relatively small: x lies in the range 0.74-0.80 (+/- 0.05) for 1 and 0.23-0.28 (+/- 0.05) for 2. Thermal investigation of 1 and 2 by thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) shows that both materials transform to gamma-(CoxZn(1-x))3(PO4)2 when heated to 518 and 435 degrees C, respectively, with enthalpy changes for complete dehydration of DeltaH= 41.9 and 53.5 kJ mol(-1), respectively. Dehydration of 1 occurs in a single irreversible step, while that of 2 occurs over a greater temperature range and proceeds via several steps. A new phase, (CoxZn(1-x))3(PO4)2.0.27H2O, is formed when 2 is heated to 357 degrees C.