Thermal stability of stercorite H(NH<Subscript>4</Subscript>)Na(PO<Subscript>4</Subscript>)·4H<Subscript>2</Subscript>O

Thermogravimetric analysis has been used to determine the thermal stability of the mineral stercorite H(NH₄)Na(PO₄)·4H₂O. The mineral stercorite originated from the Petrogale Cave, Madura, Eucla, Western Australia. This cave is one of many caves in the Nullarbor Plain in the South of Western Australia. The mineral is formed by the reaction of bat guano chemicals on calcite substrates. Upon thermal treatment the mineral shows a strong decomposition at 191 °C with loss of water and ammonia. Other mass loss steps are observed at 158, 317 and 477 °C. Ion current curves indicate a gain of CO₂ at higher temperature and are attributed to the thermal decomposition of calcite impurity.     

Crystal structure of Na<Subscript>3</Subscript>(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>[Ir(SO<Subscript>3</Subscript>)<Subscript>2</Subscript>Cl<Subscript>4</Subscript>]·4H<Subscript>2</Subscript>O

The complex Na₃(NH₄)₂[Ir(SO₃)₂Cl₄]·4H₂O was examined with single crystal X-ray diffraction and IR spectroscopy. Crystal data: a = 7.3144(4) Å, b = 10.0698(5) Å, c = 12.3748(6) Å, β = 106.203(1)°, V = 875.26(8) ų, space group P2₁/c, Z = 2, d _calc = 2.547 g/cm³. In the complex anion two trans SO ₃ ^2? groups are coordinated to iridium through the S atom. The splitting of O-H bending vibrations of crystallization water molecules and N-H ones of the ammonium cation is considered in the context of different types of interactions with the closest neighbors in the structure.     

Preparation of Li<Subscript>9</Subscript>Cr<Subscript>3</Subscript>(P<Subscript>2</Subscript>O<Subscript>7</Subscript>)<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript> as cathode material for lithium ion batteries through sol–gel method

The compound Li₉Cr₃(P₂O₇)₃(PO₄)₂ has been successfully synthesized using sol–gel method. X-ray diffraction Rietveld refinement analysis indicates that single phase Li₉Cr₃(P₂O₇)₃(PO₄)₂ can be obtained under air condition and high purity nitrogen atmosphere. Scanning electron microscopy indicates that nanowires with lengths ranging from several to tens micrometers and diameters varying from 100nm to 500nm can be obtained in the Li₉Cr₃(P₂O₇)₃(PO₄)₂ compound heated under air condition. The electrochemical properties of Li₉Cr₃(P₂O₇)₃(PO₄)₂ sintered under N₂ as cathode material is reported for the first time. The XRD patterns of the electrodes before and after 30 cycles indicate that the Li₉Cr₃(P₂O₇)₃(PO₄)₂ keeps its original monodiphosphate structure.     

Thermal stability of crandallite CaAl<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>(OH)<Subscript>5</Subscript>·(H<Subscript>2</Subscript>O)

Thermogravimetry combined with evolved gas mass spectrometry has been used to characterise the mineral crandallite CaAl₃(PO₄)₂(OH)₅·(H₂O) and to ascertain the thermal stability of this ‘cave’ mineral. X-ray diffraction proves the presence of the mineral and identifies the products of the thermal decomposition. The mineral crandallite is formed through the reaction of calcite with bat guano. Thermal analysis shows that the mineral starts to decompose through dehydration at low temperatures at around 139 °C and the dehydroxylation occurs over the temperature range 200–700 °C with loss of the OH units. The critical temperature for OH loss is around 416 °C and above this temperature the mineral structure is altered. Some minor loss of carbonate impurity occurs at 788 °C. This study shows the mineral is unstable above 139 °C. This temperature is well above the temperature in the caves of 15 °C maximum. A chemical reaction for the synthesis of crandallite is offered and the mechanism for the thermal decomposition is given.     

Non-isothermal kinetics of thermal decomposition of NH<Subscript>4</Subscript>ZrH(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>·H<Subscript>2</Subscript>O

Nanocrystalline NH₄ZrH(PO₄)₂·H₂O was synthesized by solid-state reaction at low heat using ZrOCl₂·8H₂O and (NH₄)₂HPO₄ as raw materials. X-ray powder diffraction analysis showed that NH₄ZrH(PO₄)₂·H₂O was a layered compound with an interlayer distance of 1.148 nm. The thermal decomposition of NH₄ZrH(PO₄)₂·H₂O experienced four steps, which involves the dehydration of the crystal water molecule, deamination, intramolecular dehydration of the protonated phosphate groups, and the formation of orthorhombic ZrP₂O₇. In the DTA curve, the three endothermic peaks and an exothermic peak, respectively, corresponding to the first three steps' mass losses of NH₄ZrH(PO₄)₂·H₂O and crystallization of ZrP₂O₇ were observed. Based on Flynn–Wall–Ozawa equation and Kissinger equation, the average values of the activation energies associated with the NH₄ZrH(PO₄)₂·H₂O thermal decomposition and crystallization of ZrP₂O₇ were determined to be 56.720 ± 13.1, 106.55 ± 6.28, 129.25 ± 4.32, and 521.90 kJ mol⁻¹, respectively. Dehydration of the crystal water of NH₄ZrH(PO₄)₂·H₂O could be due to multi-step reaction mechanisms: deamination of NH₄ZrH(PO₄)₂ and intramolecular dehydration of the protonated phosphate groups from Zr(HPO₄)₂ are simple reaction mechanisms.     

Crystal structure of [Pb<Subscript>3</Subscript>(OH)<Subscript>4</Subscript>Co(NO<Subscript>2</Subscript>)<Subscript>3</Subscript>](NO<Subscript>3</Subscript>)(NO<Subscript>2</Subscript>)·2H<Subscript>2</Subscript>O

The structure of [Pb₃(OH)₄Co(NO₂)₃](NO₃)(NO₂)·2H₂O is determined by single crystal X-ray diffraction. The crystallographic characteristics are as follows: a = 8.9414(4) Å, b = 14.5330(5) Å, c = 24.9383(9) Å, V = 3240.6(2) ų, space group Pbca, Z = 8. The Co(III) atoms have a slightly distorted octahedral coordination formed by three nitrogen atoms belonging to nitro groups (Co–N_av is 1.91 Å) and three oxygen atoms belonging to hydroxyl groups (Co–O_av is 1.93 Å). The hydroxyl groups act as μ₃-bridges between the metal atoms. The geometric characteristics are analyzed and the packing motif is determined.     

Glass Formation in the Al<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>–(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>SO–H<Subscript>2</Subscript>O System

The glass formation in the Al₂(SO₄)₃–(CH₃)₂SO–H₂O system was found for the first time. The competitive ability of ligands, dimethyl sulfoxide and water (which are strong donors), for entering the first coordination sphere of aluminum is considered. The possibility of mixed coordination of (CH₃)₂SO (via sulfur and oxygen atoms) in the first coordination sphere of aluminum with retention of the glass-forming ability of the sample was suggested on the basis of IR spectral study.     

Synthesis and study of uranyl arsenate (UO<Subscript>2</Subscript>)<Subscript>3</Subscript>(AsO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 12H<Subscript>2</Subscript>O

A method for producing synthetic troegerite of composition(UO₂)₃(AsO₄)₂ · 12H₂. Owas developed. X-ray diffraction, IR spectrometry, X-ray fluorescence analysis, and scanning calorimetry were used to study its dehydration and thermal decomposition, to solve the structgure, and to determine X-ray diffraction and IR spectroscopic characteristics.     

Synthesis and isoconversional kinetic study of the formation of LiNiPO<Subscript>4</Subscript> from Ni<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>·8H<Subscript>2</Subscript>O as a new precursor

The nanosized LiNiPO₄ was successfully synthesized by a solid-state reaction between the new Ni₃(PO₄)₂·8H₂O precursor and Li₃PO₄ at 700 °C in air atmosphere. The formation of LiNiPO₄ was generated via three thermal decomposition steps. The samples were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, atomic absorption/atomic emission spectrophotometers, and thermogravimetric/differential thermal gravimetric/differential thermal analysis techniques. The activation energy (E_α) values of the three steps were calculated by Vyazovkin method and determined to be 90.39?±?5.79, 197.81?±?7.46, and 308.66?±?12.03 kJ mol^?1, respectively. The average E_α values from this method are very close to E_α from KAS method. The most probable mechanism functions g(α) of three steps were evaluated by using the masterplots method and found to be the F_1/3 (first step), F_3/2 (second step), and D₄ (final step), respectively. The pre-exponential factors (A) values of three steps were obtained based on the E_α and g(α). The kinetic triplet parameters of the formation of LiNiPO₄ from the new precursor are reported in the first time.     

Phase formation in the system Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>–MgMoO<Subscript>4</Subscript>–Sc<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>

Phase formation in the system Li₂MoO₄–MgMoO₄–Sc₂(MoO₄)₃ was studied by X-ray powder diffraction analysis and differential thermal analysis. Ternary molybdate LiMgSc(MoO₄)₃ was synthesized, which crystallizes in the triclinic system (space group P\(\bar 1\)). In the Li₂Mg₂(MoO₄)₃–Li₃Sc(MoO₄)₃ section, a continuous solid solution in the rhombic system was found to form (space group Pnma).     

Blue and green upconversion luminescence modification of Tb<Superscript>3+</Superscript>–Yb<Superscript>3+</Superscript> co-doped Ca<Subscript>5</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>F inverse opal

Tb³⁺–Yb³⁺ co-doped Ca₅(PO₄)₃F inverse opal photonic crystals were prepared by a self-assembly technique in combination with a sol–gel method. Upconversion luminescence characteristics of the inverse opals were investigated. The results indicate that photonic band gap has a significant effect on upconversion luminescence of Tb³⁺–Yb³⁺ co-doped Ca₅(PO₄)₃F inverse opal. Significant inhibition of the green or blue upconversion luminescence was inspected if the photonic band gap overlapped with the emission band of Tb³⁺ ions.     

Synthesis and structure of the complex [Mo<Subscript>3</Subscript>(μ<Subscript>3</Subscript>-S)(μ<Subscript>2</Subscript>-S<Subscript>2</Subscript>)<Subscript>3</Subscript>(Et<Subscript>2</Subscript>NCS<Subscript>2</Subscript>)<Subscript>3</Subscript>]I

The structure of tri-μ₂-disulfido-μ₃-thiotris(diethyldithiocarbamato)-S,S′-triangle-trimolybdenum iodide [Mo₃(μ₃-S)(μ₂-S₂)₃(Et₂NCS₂)₃]I was determined. The compound was characterized by differential thermal analysis and IR, Raman, and X-ray electronic spectroscopy.     

Simple thermal decomposition method to synthesize LiTi<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C core–shell composite for lithium ion batteries

Polyanionic LiTi₂(PO₄)₃ material with 3D framework structure is intensively investigated to be used in lithium ion batteries. However, the LiTi₂(PO₄)₃-based materials suffer from poor electronic conductivity hindering the application as electrode active materials. This work describes an effective and simple strategy to synthesize LiTi₂(PO₄)₃/C core–shell structure without the addition of external carbon sources. This approach is achieved by a simple one-step solid state reaction using organometallic salt as raw material. The as-prepared LiTi₂(PO₄)₃ exhibits uniform and thin carbon coating on the particle surface. The electrochemical properties of the LiTi₂(PO₄)₃/C composite are investigated, and the results demonstrate that the as-prepared LiTi₂(PO₄)₃/C shows good cycling performance and rate capability.     

High-temperature heat capacity of Pb<Subscript>8</Subscript>La<Subscript>2</Subscript>(GeO<Subscript>4</Subscript>)<Subscript>4</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript> in the range 320–1000 K

The oxide compound Pb₈La₂(GeO₄)₄(VO₄)₂ with an apatite structure has been synthesized by a ceramic method. The effect of temperature on the molar hear capacity of polycrystalline samples in the temperature range 320–1000 K has been studied by differential scanning calorimetry. The results have been used to calculate the thermodynamic functions of the synthesized compound.     

Crystal structure of Cs[(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>(OH)] · H<Subscript>2</Subscript>O

Single crystals of Cs[(UO₂)₂(C₂O₄)₂(OH)] · H₂O were synthesized and structurally studied using X-ray diffraction. The compound crystallizes in monoclinic space group P2₁/m, Z = 2, with the unit cell parameters a = 5.5032(4) Å, b = 13.5577(8) Å, c = 9.5859(8) Å, β = 97.012(3)°, V = 709.86(9) ų, R = 0.0444. The main building units of crystals are [(UO₂)₂(C₂O₄)₂(OH)]^? layers of the A₂K ₂ ⁰² M² (A = UO ₂ ²⁺ , K⁰² = C₂O ₄ ^2? , and M² = OH^?) crystal-chemical family. Uranium-containing layers are linked into a three-dimensional framework via electrostatic interactions with outer-sphere cations and hydrogen bonds with water molecules.     

Thermal analysis of the (Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>1−x</Subscript>(Y<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>x</Subscript> pigments

The synthesis of new compounds based on Bi₂O₃ is investigated because they can be used as new ecological inorganic pigments. Chemical compounds of the (Bi₂O₃)_1−x(Y₂O₃)_x type were synthesized. The host lattice of these pigments is Bi₂O₃ that is doped by Y³⁺ ions. The incorporation of doped ions provides the interesting colours and contributes to a growth of the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. This paper also contains the results of the pigment characterization by X-ray powder diffraction and their colour properties.     

Rapid synthesis,kinetics and thermodynamics of binary Mn<Subscript>0.5</Subscript>Ca<Subscript>0.5</Subscript>(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript> · H<Subscript>2</Subscript>O

The non-isothermal kinetics of dehydration of AlPO₄·2H₂O was studied in dynamic air atmosphere by TG–DTG–DTA at different heating rates. The result implies an important theoretical support for preparing AlPO₄. The AlPO₄·2H₂O decomposes in two step reactions occurring in the range of 80–150 °C. The activation energy of the second dehydration reaction of AlPO₄·2H₂O as calculated by Kissinger method was found to be 69.68 kJ mol⁻¹, while the Avrami exponent value was 1.49. The results confirmed the elimination of water of crystallization, which related with the crystal growth mechanism. The thermodynamic functions (ΔH*, ΔG* and ΔS*) of the dehydration reaction are calculated by the activated complex theory. These values in the dehydration step showed that it is directly related to the introduction of heat and is non-spontaneous process.     

TeO<Subscript>2</Subscript>–(NaPO<Subscript>3</Subscript>)<Subscript>6</Subscript> Glass-Forming System

It is suggested to use sodium hexametaphosphate as a new glass-forming agent for tellurite glasses. The limits of the glass-forming region were determined for the TeO₂–(NaPO₃)₆ system, and a selective study of the thermal behavior of the glasses synthesized was carried out by the method differential scanning calorimetry. The optical transmission in the UV, visible, and IR spectral ranges was examined. It was shown that oxides of rare-earth elements can be introduced into the glass, which opens up prospects for application of the system as a matrix for generation of laser light in the 2-μm range, required in fabrication of medical lasers.     

Crystal structure of [(C<Subscript>6</Subscript>H<Subscript>5</Subscript>)<Subscript>4</Subscript>P][Ni(B<Subscript>9</Subscript>C<Subscript>2</Subscript>H<Subscript>11</Subscript>)<Subscript>2</Subscript>]·CCl<Subscript>4</Subscript>

A new compound containing the tetraphenylphosphonium cation and the nickel(III) bisdicarbollyl anion, [(C₆H₅)₄P][Ni(B₉C₂H₁₁)₂]·CCl₄, was synthesized and investigated by XRD at room temperature (295 K). Crystal data: C₂₉H₄₂B₁₈PCl₄Ni, M = 816.69, monoclinic, space group P2/c; unit cell parameters a = 13.5873(6) Å, b = 7.1475(2) Å, c = 20.7829(8) Å, β = 94.4595(13)°, V = 2012.2(2) ų, Z = 2, d _calc = 1.348 g/cm³. The structure was solved by direct and Fourier methods and refined by the full-matrix least squares method in an anisotropic (isotropic for H) approximation to the final R ₁ = 0.0466 for 3055 I _hkl ≥ 2σ _I of 23,655 reflections collected and 5618 independent I _hkl (Bruker X8 APEX diffractometer, λMoK _α).