Synthesis and characterization of a new layered magnesium zinc phosphate hydrate

A new layered magnesium zinc phosphate hydrate, MgZn(HPO₄)₂·H₂O, with a zinc phosphate framework isostructural with the one of Na₂Zn(HPO₄)₂·4H₂O, was prepared by the direct ambient pressure and temperature reaction between zinc 2,4-pentanedionate, phosphoric acid and hexahydrated magnesium chloride. The as-prepared sample is monoclinic (a = 8.780(7) Å, b = 13.240(7) Å, c = 11.123(0) Å and β = 116.21(2)°). The prepared solid undergoes two thermal transformations when it is heated from 110 to 600 °C. The first transformation is due to the release of intercalated water molecules and the second one is due to the HPO₄²⁻ → P₂O₇⁴⁻ transition.     

Synthesis and crystal structure of a novel lithium bismuth phosphate, Li2Bi14.67(PO4)6O14

A lithium bismuth phosphate, Li₂Bi_14.67(PO₄)₆O₁₄, has been synthesized for the first time by the solid-state method. The crystal structure was determined by single crystal X-ray diffraction at 150 K. Li₂Bi_14.67(PO₄)₆O₁₄ crystallizes in the monoclinic system C2/c (No. 15), with a = 30.8189(4) Å, b = 5.2691(3) Å, c = 24.5302(3) Å, β = 122.84(2)°, V = 3346.81(1) Å³ and Z = 2. The structure along the b axis consists of layers of [Bi₂O₂] units as the basic building block. These are separated by isolated PO₄ and LiO₄ tetrahedra. The oxygen co-ordination around two of the phosphorus atoms is disordered. Solid-state ⁷Li NMR studies confirm the presence of lithium in the structure. The material shows ionic conductivity of the order of 10⁻⁵ S cm⁻¹ at 600 °C.     

Transformation of Dion-Jacobson phase to Aurivillius phase: synthesis of (PbBiO2)MNb2O7 (M = La, Bi)

We describe transformations of the Dion-Jacobson (D-J) phases, KLaNb₂O₇ and RbBiNb₂O₇, to the Aurivillius (A) phases, (PbBiO₂)LaNb₂O₇ (1) and (PbBiO₂)BiNb₂O₇ (2), in a metathesis reaction with PbBiO₂Cl. Oxide 1 adopts centrosymmetric tetragonal structure (a = 3.905(1) Å, c = 25.66(1) Å), whereas oxide 2 crystallizes in a noncentrosymmetric orthorhombic (A2₁am) (a = 5.489(1) Å, b = 5.496(2) Å, c = 25.53(1) Å) structure. Oxide 2 shows a distinct SHG response towards 1064 nm laser radiation. The role of La³⁺ versus Bi³⁺ in the perovskite slabs for the occurrence of noncentrosymmetric structure/ferroic property in these materials is pointed out.     

Reinvestigation of the binary diagram Na3PO4-FePO4 and crystal structure of a new iron phosphate Na3Fe3(PO4)4

A new iron(III) phosphate Na₃Fe₃(PO₄)₄ has been synthesized and characterized. It decomposes before melting at 860°C into FePO₄ and Na₃Fe₂(PO₄)₃. The structure of the compound was determined by single-crystal X-ray diffraction. The unit cell is monoclinic with the following parameters: a=19.601(8) Å, b=6.387(1) Å, c=10.575(6) Å and β=91.81(4)°; Z=4; space group: C2/c. Na₃Fe₃(PO₄)₄ exhibits a layered structure involving corner-linkage between FeO₆ octahedra, and corner- and edge-sharing between FeO₆ octahedra and PO₄ tetrahedra. The Na⁺ cations occupying the interlayer space are six- and seven-fold coordinated by oxygen atoms. The relationship between the structure of Na₃Fe₃(PO₄)₄ and the previous reported hydrate K₃Fe₃(PO₄)₄·H₂O will be discussed.     

Synthesis of the new layered oxides NaRbLnMO5 (Ln = La, Nd, Sm, Eu, Gd; M = Nb, Ta)

The new layered transition metal oxides NaRbLnMO₅ (Ln = Nd, Sm, Eu, Gd; M = Nb, Ta) were synthesized by direct solid-state reaction. NaRbLaNbO₅ crystallizes with a tetragonal unit cell [a=5.839(6) Å, c=8.313(1) Å] analogous to that of the related compound NaKLaNbO₅, while NaRbLaTaO₅ indexes to a larger monoclinic unit cell [a=9.577(2) Å, b=5.834(1) Å, c=8.323(2) Å, β=93.00(2)]. NaRbLnNbO₅ can be prepared for Ln = Nd, Sm, Eu, Gd, and NaRbLnTaO₅ can be prepared for Ln = Nd, Sm. Both series of compounds show the expected decrease in unit cell volume as the size of the lanthanide decreases. NaRbLaNbO₅ is also amenable to ion exchange, forming Li_2−xRb_xLaNbO₅ upon reaction with molten lithium nitrate.     

Synthesis, crystal structure and magnetic properties of a new lithium cobalt metaphosphate, LiCo(PO3)3

A new lithium cobalt metaphosphate, LiCo(PO₃)₃, is reported for the first time, which was discovered during the exploratory synthesis in Li-Co-P-O system by solid state reaction. The structure has been refined by powder X-ray Rietveld refinement method (P2₁2₁2₁, a = 8.5398(2) Å, b = 8.6326(2) Å and c = 8.3520(2) Å, Z = 4, R_p = 13.6%, R_wp = 19.4%, R_exp = 17.7%, S = 1.11, χ² = 1.23). It is isostructural with LiM(PO₃)₃ (M = Fe, Cu). It contains (PO₃)¹⁻ chains with the Co atoms localized in the octahedral sites, bridging four neighboring chains. The magnetic susceptibility measurement showed a typical paramagnetic behavior of high spin of Co²⁺, following the Curie-Weiss law in the temperature range of 5-300 K. Unlike the olivine type lithium cobalt phosphate, LiCoPO₄, cyclic voltammetry of LiCo(PO₃)₃ assembled in the coin-type cell showed no electrochemical activity in the voltage region of 1-5 V versus Li/Li⁺.     

Crystal growth and structure refinement of monoclinic Li2TiO3

Colorless platelet crystals of monoclinic Li₂TiO₃ with a maximum size of 5.0 mm × 5.0 mm × 0.5 mm were successfully grown by a flux method at 1373 K using a LiBO₂-Li₂O system flux. The stoichiometric chemical composition of Li₂TiO₃ was determined by the SEM-EDX, ICP-AES and density measurement using the single crystal samples. The thermal conductivity of the Li₂TiO₃ single crystals was evaluated using hot-disk method. A single-crystal X-ray diffraction study confirmed the monoclinic Li₂SnO₃-type structure, space group C2/c and the lattice parameters of a = 5.0623(5) Å, b = 8.7876(9) Å, c = 9.7533(15) Å, β = 100.212(11)°, and V = 427.01(9) Å³. The crystal structure was refined to the conventional values of R = 2.4% and wR=3.3% for 2187 independent observed reflections. The cationic arrangement of (LiTi₂) layers in Li₂TiO₃ was precisely revealed by the structure analysis.     

A powder X-ray diffraction refinement of the BaNd2Ti3O10 structure

The structure parameters of BaNd₂Ti₃O₁₀ were refined based on Olsen’s model. This material has a monoclinic unit cell with space group P2₁/m. The unit cell parameters are: a=7.73030(14) Å, b=7.62578(14) Å, c=14.23174(31) Å, β=97.832(6)°. The structure can be considered as a layered perovskite-like structure, in which the perovskite block shows distortion. The various layers link in the order of (Ba_1/2O)-(Ba_1/2TiO₃)-(NdTiO₃)-(NdTiO₃).     

Crystal growth and structure determinations of potassium hafnates: K2Hf2O5 and K4Hf5O12

Crystals of K₂Hf₂O₅ and K₄Hf₅O₁₂ were grown from molten potassium hydroxide flux. The crystal structures were determined by single-crystal X-ray diffraction. K₂Hf₂O₅ crystallizes in the space group Pnna of the orthorhombic system, with unit cell dimensions of a = 5.780(1) Å, b = 10.640(2) Å, and c = 8.666(2) Å. This compound contains infinite chains of HfO₆ octahedra that form a channel structure. K₄Hf₅O₁₂ crystallizes in the space group of the trigonal system, with unit cell dimensions of a = 5.7877(2) Å and c = 10.3693(7) Å. This compound possesses a layered structure with six-coordinate Hf in three different coordination environments (trigonal prismatic, distorted octahedral, and regular octahedral).     

Synthesis, crystal structure, and properties of novel perovskite oxychalcogenides, Ca2CuFeO3Ch (Ch = S, Se)

Two new perovskite oxychalcogenides, Ca₂CuFeO₃S and Ca₂CuFeO₃Se, have been synthesized in evacuated quartz tubes. They crystallize in P4/nmm space group with lattice parameters a = 3.8271(1), c = 14.9485(2) Å and a = 3.8605(1), c = 15.3030(2) Å for Ca₂CuFeO₃S and Ca₂CuFeO₃Se, respectively. They appear to be the first layered chalcogenide perovskites involving calcium and are structural analogs of the corresponding Sr and Ba compounds. The new compounds exhibit semiconducting properties with energy gap decreasing from the oxysulfide to the oxyselenide. Possibility of introducing Ca²⁺ into structures of known layered oxychalcogenides and oxypnictides is discussed.     

Crystal structure, thermal analysis and IR spectrometric investigation of bis(o-anisidinium) sulfate (C7H10NO)2SO4

Chemical preparation, X-ray single-crystal, thermal behaviour, and IR spectroscopy investigations are given for a new organic cation sulfate (C₇H₁₀NO)₂SO₄ (denoted BOAS) in the solid state. This compound crystallizes in the monoclinic space group P2₁/c. The unit cell dimensions are: a = 7.010(3) Å, b = 11.142(5) Å, c = 20.770(8) Å, β = 95.27(3)° with V = 1615.4(12) Å³ and Z = 4. The structure has been solved using a direct method and refined to a reliability R factor of 0.047. The title compound consists of a framework of isolated SO₄ tetrahedral interleaved with organic molecules, so as to build isolated ribbons parallel to a-axis. In the present work, we describe the crystal structure, thermal behaviour and IR analysis of this new compound.     

Apatite phosphates containing heterovalent cations and their application in Knoevenagel condensation

Apatite structure type ortho phosphates of the formula NaLaCa₃(PO₄)₃OH and NaLaSr₃(PO₄)₃OH have been synthesized via a simple solution route. The compounds are isostructural with calcium hydroxyapatite. The phases are characterized by powder X-ray diffraction method and infrared spectroscopy. The unit cell parameters are: for NaLaCa₃(PO₄)₃OH, a = 9.457(3) and c = 6.90(1) Å and for NaLaSr₃(PO₄)₃OH, a = 9.720(3) and c = 7.23(3) Å, respectively. Knoevenagel condensation of selected aldehydes and molecules with activated methylene group is carried out using the phosphates as solid supports. Both phases facilitated the condensation reaction at room temperature in the absence of a solvent. An increase in the yield of the products is noticed when the supports are used with water.     

Synthesis and characterization of a new monophosphate (5-Cl-2,4-(OCH3)2C6H2NH3)H2PO4

Chemical preparation, crystal structure and NMR spectroscopy of a new organic cation 5-chloro(2,4-dimethoxy)anilinium monophosphate H₂PO₄ are given. This new compound crystallizes in the monoclinic system, with the space group P2₁/c and the following parameters: a = 5.524(2) Å, b = 9.303(2) Å, c = 23.388(2) Å, β = 90.66(4), V = 1201.8(2) Å³, Z = 4 and D_x = 1.573 g cm⁻³. Crystal structure has been determined and refined to R = 0.031 and R_w = 0.080 using 1702 independent reflections. Structure can be described as an infinite (H₂PO₄)_nⁿ⁻ corrugated chains in the a-direction. The organic groups (5-Cl-2,4-(OCH₃)₂C₆H₂NH₃)⁺ are anchored between adjacent polyanions through multiple hydrogen bonds. This compound is also investigated by IR, thermal, and solid-state, ¹³C, ³¹P MAS NMR spectroscopies.     

Synthesis and characterization of a new 2,4,6-triaminopyridinium dihydrogendiphosphate dihydrate (C4H8N5)2H2P2O7·2H2O

Structural properties of the 2,4,6-triaminopyridinium dihydrogendiphosphate dihydrate are discussed on the basis of an X-ray structure investigation. (C₄H₈N₅)₂H₂P₂O₇·2H₂O is monoclinic, C2/c, with a = 10.414(1) Å, b = 13.365(1) Å, c = 13.736(2) Å, β = 98.39(4)°, and Z = 4. The structure has been solved by a direct method and refined to a reliability R factor of 0.0375 (R_w = 0.0961) using 2751 independent reflections. The structural arrangement can be described as inorganic infinite ribbons, , spreading along the c direction; the organic groups, [C₄H₈N₅]⁺, link the precedent ribbons, via their hydrogen bonds, to form a three-dimensional network. The present work, deals with crystal structure, thermal behavior and IR analysis of this new compound.     

Synthesis and crystal sructure of a new dihydrogenomonophosphate (4-C2H5C6H4NH3)H2PO4

Chemical preparation, crystal structure, calorimetric, and spectroscopic investigations are given for a new organic-cation dihydrogenomonophosphate, (4-C₂H₅C₆H₄NH₃)H₂PO₄ in the solid state. This compound crystallizes in the orthorhombic space group Pbca with the following unit cell parameters: a=8.286(3) Å, b=9.660(2) Å, c=24.876(4) Å, Z=8, V=1991.2(7) Å³, and D_X=1.442 g cm⁻³. Crystal structure was solved with a final R=0.054 for 3305 independent reflections. The atomic arrangement coaled described as H₂PO₄⁻ layers between which are located the 4-ethylanilinium cations.     

Crystal structure and physicochemical properties of a new organic condensed phosphate (C7H10NO)3P3O9·4H2O

Chemical preparation, X-ray characterization, IR spectroscopy and thermal analysis of a new cyclotriphosphate: (C₇H₁₀NO)₃P₃O₉·4H₂O abbreviated as OACTP, are reported. This mixed organo-mineral compound crystallizes in the monoclinic system with P2₁/n space group, the unit cell dimensions are: a = 6.605(3) Å, b = 26.166(3) Å, c = 18.671(8) Å, β = 91.95(3)°, Z = 4 and V = 3255(2) Å³. The structure was solved using a direct method and refined to a reliability R-factor of 0.043 using 3931 independent reflections (I > 2σI). Atomic arrangement exhibits infinite (P₃O₉·2H₂O)_n³ⁿ⁻ chains connected by organic cations. The thermal behavior and the IR spectroscopic studies of this new compound are discussed.     

High temperature-induced phase transitions in Sr2GdRuO6 complex perovskite

The crystal structure behavior of the Sr₂GdRuO₆ complex perovskite at high-temperature has been investigated over a wide temperature range between 298 K ≤ T ≤ 1273 K. Measurements of X-ray diffraction at room-temperature and Rietveld analysis of the experimental patterns show that this compound crystallizes in a monoclinic perovskite-like structure, which belongs to the P2₁/n (#14) space group and 1:1 ordered arrangement of Ru⁵⁺ and Gd³⁺ cations over the six-coordinate M sites. Experimental lattice parameters were obtained to be a =5.8103(5) Å, b =5.8234(1) Å, c =8.2193(9) Å, V = 278.11(2) Å³ and angle β = 90.310(5)°. The high-temperature analysis shows the occurrence of two-phase transitions on this material. First, at 573 K it adopts a monoclinic perovskite-type structure with I2/m (#12) space group with lattice parameters a = 5.8275(6) Å, b = 5.8326(3) Å, c = 8.2449(2) Å, V = 280.31(3) Å³ and angle β = 90.251(3)°. Close to 1273 K it undergoes a complete phase-transition from monoclinic I2/m (#12) to tetragonal I4/m (#87), with lattice parameters a = 5.8726(1) Å, c = 8.3051(4) Å, V = 286.39(8) Å³ and angle β = 90.0°. The high-temperature phase transition from monoclinic I2/m (#12) to tetragonal I4/m (#87) is characterized by strongly anisotropic displacements of the anions.     

Crystal structure and magnetic properties of double perovskite Mn2FeSbO6

The double perovskite Mn₂FeSbO₆ has been synthesized under pressure 6 GPa and temperature 1000 °C. The crystal structure refinement of Mn₂FeSbO₆ was carried out with the GSAS program suite using X-ray diffraction data. XRD pattern of Mn₂FeSbO₆ was indexed with a monoclinic unit cell (space group P2₁/n) with parameters: a = 5.2431(3) Å, b = 5.3935(3) Å, c = 7.6358(5) Å, β = 89.693(2)°, V = 215.927 Å³, Z = 2. It found that Fe and Sb atoms are completely ordered in 2d and 2c positions of double perovskite structure respectively. According to XPS measurements, manganese in this compound is present as Mn²⁺, whiles the iron - as Fe³⁺. Magnetization measurements revealed the presence about 3 mass% of ferromagnetic impurity in the sample. Dependence of AC susceptibility χ″ from temperature showed that magnetic properties compound are determined probably by transformation in antiferromagnetic state below 19.5 K.     

PEG-300 assisted hydrothermal synthesis of 4ZnO·B2O3·H2O nanorods

4ZnO·B₂O₃·H₂O is commonly used as a flame-retardant filler in composite materials. The microstructure of the powder is of importance in its applications. In our study, for the first time, one-dimensional (1D) nanostructure of 4ZnO·B₂O₃·H₂O with rectangle rod-like shape has been synthesized by a hydrothermal route in the presence of surfactant polyethylene glycol-300 (PEG-300). The nanorods have been characterized by X-ray powder diffraction (XRD), inductively coupled plasma with atomic emission spectroscopy (ICP-AES), thermogravimetry (TG) and differential thermal analysis (DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with selected area electron diffraction (SAED) as well as high-resolution transmission electron microscopy (HRTEM). These nanorods are about 70 nm in thickness, 150-800 nm in width and have lengths up to a few microns. 4ZnO·B₂O₃·H₂O nanorods crystallize in the monoclinic space group P2₁/m, a = 6.8871(19) Å, b = 4.9318(10) Å, c = 5.7137(16) Å, β = 98.81(21)° and V = 191.779(71) Å³.     

Effect of doping with Nd ions on the structural and ferroelectric properties of Ca0.28Ba0.72Nb2O6 single crystal

The crystal structure of Ca_0.28Ba_0.72Nb₂O₆ (CBN-28) crystal with Nd-doping has been determined from X-ray single crystal diffraction data, in the tetragonal system with space group P4bm and the following parameters: a = b = 12.458 Å, c = 3.954 Å, V = 613.688 Å³, and Z = 5. X-ray diffraction results on a Nd-doped CBN-28 single crystal also have demonstrated that Nd³⁺ and Ca²⁺ occupy the same site in the crystal structure. Dielectric and ferroelectric measurements have been performed. Transition from ferroelectric to paraelectric at around 223 °C has been observed. The Nd-doped crystal has a lower Curie temperature (T_m) than that of undoped CBN-28 crystal. The spontaneous polarization (P_s) and coercive electric field (E_c) also decrease compared with their values in the undoped CBN-28 crystal.