Phase formation in the ZrO(NO3)2-NaF(HF)-H3PO4-H2O system at 20°C

Phase formation in the ZrO(NO₃)₂-NaF(HF)-H₃PO₄-H₂O system was studied at 20°C and 2.0–14.5 wt % ZrO₂ in the initial solution along sections with molar ratios PO ₄ ^3? /Zr = 0.5 and 1.5 and also in the presence of hydrogen fluoride at Na/Zr = 1 and PO ₄ ^3? /Zr = 0.5, 1.0, and 1.5. Crystalline zirconium hydrophosphate Zr(HPO₄)₂ · H₂O, fluorozirconates Na₅Zr₂F₁₃ and Na₇Zr₆F₃₁ · 12H₂O, fluorophosphatozirconates NaH₂Zr₃F₃(PO₄)₄ · 3H₂O and NaZr₂F₆(PO₄) · 4H₂O, and amorphous NaZrO_0.5F(PO₄) · 4H₂O (provisional composition) were separated at room temperature. NaH₂Zr₃F₃(PO₄)₄ · 3H₂O and NaZr₂F₆(PO₄) · 4H₂O were prepared for the first time and were studied by crystal-optical, elemental, and thermal analyses, X-ray powder diffraction, IR spectroscopy, scanning electron microscopy (SEM), and X-ray microanalysis. Na₇Hf₆F₃₁ · 12H₂O was found to exist in a mixture with the hydrophosphate.     

Phase formation in the ZrO(NO3)2-H3PO4-RbF-H2O system: the PO 43? /Zr = 0.5 section

We studied phase formation in the ZrO(NO₃)₂-H₃PO₄-RbF-H₂O system along PO₄³⁻/Zr = 0.5 (mol/mol) and RbF/Zr = 1–5 (mol/mol) sections with 2–10 wt % ZrO₂ in the starting solution. We recovered amorphous rubidium oxofluorophosphatozirconate Rb₂Zr₃OF₆(PO₄)₂ · 2H₂O and the following fluorophosphatonitratozirconates: Rb₂ZrF₄(PO₄)_0.33NO₃, which forms large cubic system crystals; weakly crystallized RbZr₃OF₃(PO₄)₂(NO₃)₂ · 5H₂O; and amorphous Zr₃OF₃(PO₄)₂NO₃ · (7–8) H₂O. A shown by its IR spectrum, Rb₂ZrF₄(PO₄)_0.33NO₃ contains NO₃- and PO₄ groups that are not coordinated to zirconium, meaning that this is a triple salt ZrF₄ · Rb(PO₄)_0.33 · RbNO₃. The formula units of the RbZr₃OF₃(PO₄)₂(NO₃)₂ · 5H₂O and Zr₃OF₃(PO₄)₂NO₃ · (7–8)H₂O phases are only conventional. All compounds have been recovered for the first time.     

Phase formation in the ZrO(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-H<Subscript>3</Subscript>PO<Subscript>4</Subscript>-CsF-H<Subscript>2</Subscript>O system at low concentration of the phosphorus-containing component

The ZrO(NO₃)₂-H₃PO₄-CsF-H₂O system was studied at 20°C along the section at a molar ratio of PO₄³⁻/Zr = 0.5 (which is of the greatest interest in the context of phase formation) at ZrO₂ concentrations in the initial solutions of 2–14 wt % and molar ratios of CsF: Zr = 1−6. The following compounds were isolated for the first time: crystalline fluorophosphates CsZrF₂PO₄ · H₂O, amorphous oxofluorophosphate Cs₂Zr₃O₂F₄(PO₄)₂ · 3H₂O, and amorphous oxofluorophosphate nitrate CsZr₃O_1.25F₄(PO₄)₂(NO₃)_0.5 · 4.5H₂O. The compound Cs₃Zr₃O_1.5F₆(PO₄)₂ · 3H₂O was also isolated, which forms in a crystalline or glassy form, depending on conditions. The formation of the following new compounds was established: Cs₂Zr₃O_1.5F₅(PO₄)₂ · 2H₂O, Cs₂Zr₃F₂(PO₄)₄ · 4.5H₂O, and Zr₃O₄(PO₄)_1.33 · 6H₂O, which crystallize only in a mixture with known phases. All the compounds were studied by X-ray powder diffraction, crystal-optical, thermal, and IR spectroscopic analyses.     

Phase formation in the ZrO(NO3)2-H3PO4-CsF(HF)-H2O system

The phase formation in the system ZrO(NO₃)₂-H₃PO₄-CsF(HF)-H₂O was studied at the molar ratio CsF/Zr = 1 along the sections PO ₄ ^3? /Zr = 0.5 and 1.5 at a ZrO₂ concentration in the initial solution of 2?C14 wt %. The following compounds were isolated: Cs₅Zr₄F₂₁ · 3H₂O, CsZr₂(PO₄)₃ · 2HF · 2H₂O, CsZrF₂PO₄ · H₂O, CsZr₂F₆PO₄ · 4H₂O (for the first time), CsHZrF₃PO₄ (for the first time), Cs_0.70ZrF(PO₄)_1.23 · nH₂O, and CsHZr₂F₂(P_O4)_2.66 · nH₂O. The compositions of CsZrF₂PO₄ · H₂O, Cs_0.70ZrF(PO₄)_1.23 · nH₂O, and CsHZr₂F₂(PO₄)_2.66 · nH₂O are conditional. All the compounds were characterized by crystal-optical, X-ray powder diffraction, thermal analyses, and IR spectroscopy. The formula CsHZrF₃PO₄ was established by energy-dispersive analysis with a LEO-1450 scanning electron microscope and an MS-46 CAMECA X-ray microanalyzer.     

Thermal stability and X-ray-luminescent properties of fluorozirconates and fluorosulfatozirconates

The thermolysis of fluorozirconates (M₂ZrF₆, M₅Zr₄F₂₁ · 3H₂O, MZrF₅ · H₂O, Rb₂Zr₃OF₁₂, and Cs₂Zr₃F₁₄ · 1.5H₂O) and fluorosulfatozirconates (M₂ZrF₄SO₄, Rb₃Zr₂F₉SO₄ · 2H₂O, and Cs₈Zr₄F₂(SO₄)₁₁ · 16H₂O) with M = K, Rb, or Cs in undried air was studied by thermal analysis in tandem with X-ray powder diffraction. The X-ray luminescence (XRL) intensity was determined for these compounds and their thermolysis products. A mixture of Rb₂Zr₃OF₁₂ and Rb₂ZrF₆ luminescent phases was detected in the thermolysis products of Rb₅Zr₄F₂₁ · 3H₂O and RbZrF₅ · H₂O for the first time. After heat treatment, a considerable quantum yield was observed for ZnZrF₆ · 5H₂O, ZnZrF₆ · 6H₂O, and ZnZr₂F₁₀ · 7H₂O. The XRL luminescence was affected by the composition of the phase and the density of excited states (F* and O*).     

Thermal stability and X-ray luminescent properties of cesium fluorophosphatozirconates

Crystalline cesium fluorophosphatozirconates (CFPZs) CsZr₂F₆PO₄ · 4H₂O, CsZrF₂PO₄ · 0.5H₂O, CsH₂Zr₂F₂(PO₄)₃ · 2H₂O, and amorphous Cs₂Zr₃OF₆(PO₄)₂ · 3H₂O were synthesized, and their thermal stability and luminescence ability were studied. The compositions of initial CsH₂Zr₂F₂(PO₄)₃ · 2H₂O and Cs₂Zr₃OF₆(PO₄)₂ · 3H₂O were refined. CsZr₂O_0.5F₅PO₄, CsHZr₂F(PO₄)₃, CsZr₂(PO₄)₃, and Cs₂Zr₃OF₆(PO₄)₂ crystalline intermediates, which are comparable with BaSO₄ and CaF₂ luminophors in the context of their X-ray luminescence intensity, were recognized by thermal analysis and X-ray powder diffraction under heating.     

ZrONO3)2-H3PO4-KF(HF)-H2O system at molar ratios of PO 43? /Zr = 0.5?1.6 as the basis for phase formation

The system ZrO(NO₃)₂-H₃PO₄-KF(HF)-H₂O was studied at ∼20°C along sections at molar ratios of PO₄³⁻ = 0.5, 1.0, and 1.6; KF: Zr = 1−5; and HF: Zr = 2−6. Phases in precipitates were identified by X-ray powder diffraction; IR spectroscopy; and crystal-optical, chemical, X-ray fluorescence and thermal analyses. The following crystalline phases were isolated: potassium fluorozirconates K₃ZrF₇, K₂ZrF₆, δ-KZrF₅, and KZrF₅ · H₂O; zirconium hydrophosphate Zr(HPO₄)₂ · 0.5H₂O; and potassium fluorophosphate zirconate K₃Zr₃F₃(HPO₄)₃(PO₄)₂. The following amorphous basic oxo(hydroxo)fluorohydrophosphate nitrates were isolated: K₄Zr₄O_2.5F₈(HPO₄)₂(NO₃)₃ · 6H₂O, K₂Zr₃O₃F₂(HPO₄)₂(NO₃)₂ · H₂O, and KZr₃O_1.5F₃(HPO₄)₂(NO₃)₃ · 2H₂O. Fields of solid phases were constructed, and the roles of anions and cations in the phase formation were considered.     

Ir spectroscopic and crystal morphology studies of the structure of alakli metal fluorophosphatozirconates (hafnates)

Potassium, rhubidium, and caesium fluorophosphatozirconates (hafnates) and oxo(hydroxo)fluorophosphatonitratometalates with PO ₄ ^3? /Zr molar ratios of 2.0, 1.5, 1.0, 0.66, 0.5, and 0.33 are synthesized for the first time. Most of them form either fine crystalline or X-ray amorphous particles. In order to characterize them IR spectroscopy and SEM are used. For the crystalline compounds the types of PO₄ groups and the character of bonds between fluorine and water are revealed. The occurrence of triple MeF₄·Rb(PO₄)_0.33·RbNO₃ (Me = Zr, Hf) salts and also M₃Me₃(PO₄)₅·3HF crystalline solvates is found. The layered habit of K₃Hf₃(PO₄)₅·3HF, RbHfF₂PO₄·0.5H₂O, Rb₃Hf₃(PO₄)₅·3HF, CsHfF₂PO₄·0.5H₂O, CsHf₂F₆PO₄·4H₂O, and CsH₂Hf₂F₂(PO₄)₃·2H₂O crystals gives grounds to suppose that the structure of these compounds is layered unlike the structure of triple MeF₄·Rb(PO₄)_0.33·RbNO₃ salts.     

Phase formation along sections of the HfO(NO3)2-H3PO4-RbF-H2O system

The phase formation in the system HfO(NO₃)₂-H₃PO₄-RbF-H₂O was studied along the sections at the molar ratios PO ₄ ^3? /Hf = 0.5, 1.0, 1.5, 2.0, and 3.0 and RbF: Hf = 1?5. The initial solutions contained 2–10 wt % HfO₂. The synthesis was performed at room temperature. The following substances were obtained for the first time: crystalline fluorophosphatehafnate RbHfF₂PO₄ · 0.5H₂O, crystalline triple salt HfF₄ · Rb(PO₄)_0.33 · RbNO₃, crystalline solvate Rb₃Hf₃(PO₄)₅ · 3HF, and amorphous fluorophosphate Hf₃O₂F₂(PO₄)₂ · 8H₂O (formula is conditional). The compounds were studied by crystal-optical, elemental, X-ray diffraction, thermogravimetric, IR spectroscopic, and electron microscopic analyses.     

Structural features of acidic fluorophosphatozirconates (hafnates) from the <Superscript>19</Superscript>F, <Superscript>31</Superscript>P, <Superscript>1</Superscript>H NMR data

Fluorophosphatometallates with the composition K₃H₃Zr₃F₃(PO₄)₅, Rb₃H₃Zr₃F₃(PO₄)₅, Rb₃H₃Hf₃F₃(PO₄)₅, CsH₂Hf₂F₂(PO₄)₃?2H₂O are studied by ³¹P, ¹⁹F, and ¹H NMR. It is found that protons enter in the composition of hydrophosphate groups and fluorine atoms occupy the terminal sites in the tetravalent metal environment. Schemes of the crystal structure of fluorophosphatometallates are proposed. It is established that in CsH₂Hf₂F₂(PO₄)₃?2H₂O water molecules are bonded to the phosphate group proton via a strong hydrogen bond and are characterized by a low energy barrier of molecular motions.     

Synthesis of potassium fluorophosphate hafnates at 20°C

Potassium fluorophosphate hafnates (PFPH) K₃H₃Hf₃F₃(PO₄)₅ and KHf₂F₃(PO₄)₂ · 2H₂O were synthesized for the first time, and a KZr₂F₃(PO₄)₂ · 2H₂O phase was found to exist. The compounds were studied by crystal-optical, elemental, X-ray powder diffraction, thermogravimetric, IR spectroscopic, and electron microscopic analyses. It was found that PFPH crystallize as one-dimensional nanoparticles. The IR spectra showed that PFPH K₃H₃M₃F₃(PO₄)₅ (M = Zr, Hf) are crystal solvate K₃M₃(PO₄)₅ · 3HF. Annealing of K₃H₃Hf₃F₃(PO₄)₅ and KHf₂F₃(PO₄)₂ · 2H₂O at 1000°C gives rise to mixtures that mostly contain various phosphate hafnates.     

Phase formation in the HfO(NO3)2-H3PO4-CsF(HF)-H2O system

The phase formation in the system HfO(NO₃)₂-H₃PO₄-CsF(HF)-H₂O was studied along the sections at the molar ratios PO ₄ ^3? /Hf = 0.5, 1.5, and 2.0 and RbF:Hf = 1?C5, and also in the presence of HF at CsF: Hf = 1. The initial solutions contained 2?C24 wt % HfO₂. The synthesis was performed at room temperature. The following substances were isolated: crystalline cesium fluorophosphate hafnates CsHf₂F₆PO₄ · 4H₂O, CsHfF₂PO₄ · 0.5H₂O, and CsH₂Hf₂F₂(PO₄)₃ · 2H₂O; X-ray amorphous cesium fluorophosphate hafnate of the average composition Cs₂Hf₃O_1.5F₅(PO₄)₂ · 5H₂O; and X-ray amorphous cesium fluorophosphate nitrate hafnate Cs₅H₄Hf₃F₇(PO₄)_3.66(NO₃)₃ · 5H₂O. The compositions of the amorphous phases should be refined. Cesium fluorophosphate hafnates were obtained for the first time. The compounds were studied by crystal-optical, elemental, X-ray diffraction, IR spectroscopic, and electron microscopic analyses.     

Phase formation along the PO 4 3− /Zr = 1.5–2.0 section of the ZrO(NO3)2-KF-H3PO4-H2O) system

The phase composition of precipitates at 20°C along the PO ₄ ^3? /Zr = 1.5–2.0 section at KF/Zr = 1–5 (mol/mol) of the ZrO(NO₃)₂-H₃PO₄-KF-H₂O system has been investigated. Phases in these precipitates have been identified by X-ray powder diffraction, crystal-optical, chemical, and thermal analyses and by IR spectroscopy. The previously known potassium zirconates K₃ZrF₇ and K₂ZrF₆ have been revealed, and crystalline fluorophosphate zirconate K₃Zr₃F₃(HPO₄)₃(PO₄)₂ and a phosphate nitrate of unknown formula have been obtained for the first time.     

Thermal stability and X-ray luminescence properties of cesium fluorophosphatohafnates

The thermal stability of cesium fluorophosphatohafnates (crystalline CsHf₂F₂(HPO₄)₂PO₄ · 2H₂O, CsHfF₂PO₄ · 0.5H₂O, CsHf₂F₆PO₄ · 4H₂O and X-ray amorphous Cs₂Hf₃O_1.5F₅(PO₄)₂ · 5H₂O, Cs₅H₄Hf₃F₇(PO₄)_3.66(NO₃)₃ · 5H₂O) was determined. The weight ratios Cs⁺/Hf and PO ₄ ^3? /ZrHf in CsHf₂F₂(HPO₄)₂PO₄ · 2H₂O were confirmed by identifying the calcination production CsHf₂(PO₄)₃ (～1000°C). A new crystalline compound CsHf₂F(HPO₄)(PO₄)₂ was found by thermogravimetric and X-ray powder diffraction analysis during heating. A new method for hydrothermal synthesis of CsHf₂(PO₄)₃, which was different from the already known one, was proposed. It was ascertained that CsHf₂(PO₄)₃ possesses a significant X-ray luminescence; whereas in fluorophosphatehafnates show low luminescence intensity.     

Kinetics of H+/Na+ Ion Exchange on H1 ± xZr2 − xMx(PO4)3 (M = Y or Nb) NASICON Materials

The thermodynamic parameters of ion exchange have been estimated for HZr₂(PO₄)₃ · H₂O and the products of its aliovalent doping. Ion exchange occurs via formation of the (H₃O_{1 ? x}Na_x)Zr₂(PO₄)₃ solid-solution series. As in the case of ion exchange on layered zirconium phosphate (Zr(HPO₄)₂ · H₂O), the interdiffusion coefficient and the major interfacial defect generation processes are considerably affected by the contact-solution pH.     

Phase formation in the systems TiOCl2-H3PO4-MF(HF)-H2O (M = K, Rb, Cs)

From solutions containing 2–17 wt % TiO₂ at the molar ratios M/Ti = 1–4, F/Ti = 2–4, and PO ₄ ^3? /Ti = 0.5–10 under mild conditions, fluoro- and oxo(hydroxo) fluorophosphate titanates were isolated: crystalline M₂TiF₆ (M = K, Rb, Cs) and K₂Ti₂O_2.5F₂PO₄ · 2H₂O, and amorphous K₃Ti₄O(OH)F₇(PO₄)₃ · 5H₂O, Cs₂Ti₃O₂F₇PO₄ · 6H₂O, and CsTi₃O₃F₄PO₄ · 3H₂O. In a mixture with M₂TiF₆ and KCl, phosphate-ion-containing crystalline phases of unidentified composition were detected. The phases were studied by elemental, crystal-optical, X-ray powder diffraction, thermal, IR spectroscopic, and electron microscopic analyses. Annealing fluorophosphate titanates gives a mixture of MTiOPO₄ and TiO₂. All the mentioned alkali metal fluorophosphates contain the tetrahedral ion PO ₄ ^3? and titanium polyhedra with bonds Ti-F and Ti-O; some of them also contain bridging oxygen connecting titanium atoms: Ti-O-Ti; i.e., these substances are polymeric.     

Darstellung und Strukturbestimmung zweier Salze der Trimetaphosphimsäure,K3(PO2NH)3 und Rb3(PO2NH)3

Synthesis and Structure Determination of Two Salts of the Trimetaphosphimic Acid, K₃(PO₂NH)₃ and Rb₃(PO₂NH)₃ The reaction between P₃N₅ and the corresponding alkalimetal hydroxide monohydrate under ammonothermal conditions (6 kbar, 450 °C after 10 d) in autoclaves leads to the salts of the trimetaphosphimic acid K₃(PO₂NH)₃ resp. Rb₃(PO₂NH)₃. The structure of K₃(PO₂NH)₃ was solved by single crystals X-ray methods. The isotypic structure of Rb₃(PO₂NH)₃ was solved by X-ray powder diffraction methods. K₃(PO₂NH)₃: R3 (No. 148), a = 12.615(3) Å, c = 10.224(2) Å, Z = 6, R₁/wR₂ = 0.0276/0.0726, N(F > 2σ(F)) = 769, N(Var.) = 51.Rb₃(PO₂NH)₃: R3 (No. 148), a = 12.9971(5) Å, c = 10.5485(5), Z = 6, R_Bragg(F) = 0.0626, 289 reflections. K₃(PO₂NH)₃ and Rb₃(PO₂NH)₃ contain six-membered rings P₃N₃ substituted by oxygen which are connected to double molecules by N–H … O bridge bonds. These twinmolecules are stacked in columns which form the motive of close packed rods. K⁺ resp. Rb⁺ are between these columns. They are coordinated by 6 O which belong to 5 different rings.     

Solid-state decomposition studies on fluoroperoxo species of transition metals. Part VI. Kinetics of isothermal decomposition of M2Zr2(O2)2F6 · 2 H2O (M = Rb+, or Cs+)

The decomposition of solid fluoroperoxozirconates of alkali metals, M₂Zr₂(O₂)₂F₆ · 2 H₂O (M = Rb⁺, Cs⁺), is carried out in vacuum under isothermal conditions. The stoichiometry of the reaction may be represented by the equation, M₂Zr₂(O₂)₂F₆ · 2 H₂O(S) — M₂Zr₂O₂F₆(s) + O₂(g) + 2 H₂ O(g) (condensed). The fractional decomposition α is determined by measuring the pressure of oxygen evolved during pyrolysis with a McLeod gauge. The α values range from 0.06 to 0.70 for the rubidium and from 0.06 to 0.79 for the caesium species in the temperature ranges 107–202°C and 101–219°C, respectively. The α—time data for both compounds show that the kinetics are deceleratory throughout the course of the decomposition reaction. In both compounds, the initial stages of decomposition are described by a unimolecular decay law, while the later stages obey a contracting volume equation at all temperatures. The activation energies from Arrhenius plots are 14.0 and 10.9 kcal mole^?1 for the rubidium and 12.9 and 11.2 kcal mole^?1 for the caesium compound.     

Physicochemical Analysis of the System Zr(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>–Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>–H<Subscript>2</Subscript>SO<Subscript>4</Subscript>–H<Subscript>2</Subscript>O at 25°С

The solubility in the quaternary water–salt system Zr(SO₄)₂ · 4Н₂О–Na₂SO₄–H₂SO₄–H₂O at 25°C was studied. It was found that, in the system, there is crystallization of not only Na₂SO₄ and Zr(SO₄)₄ · 4H₂O, but also sodium sulfate zirconates Na₂Zr(SO₄)₂(OH)₂ · 0.3H₂O, Na₄Zr(SO₄)₄ · 3H₂O, and Na₂Zr(SO₄)₂ · 3H₂O and two new compounds, S₁ and S₂, which are presumably Na₂ZrO(SO₄)₂ · 2H₂O and Na₂Zr₂O₂(SO₄)₃ · 6H₂O.     

Synthesis of zirconium (hafnium) fluoride compounds and their X-ray luminescence properties

Twenty-five zirconium (hafnium) fluoride compounds have been synthesized at room temperature in the systems MO₂-H₂SO₄-M′_nA(HF)-H₂O (M = Zr (Hf); M′ = Na, K, Rb, Cs, NH₄; A = F, SO₄) and their X-ray luminescence spectra (luminescence wavelengths and relative intensities) have been measured. The X-ray luminescence of the compounds has been considered as a function of the composition (cations, anions, water content) and different structural factors (CNs, polyhedra, H-bonds). Ammonium compounds do not luminesce, and sodium fluorozirconates and heptafluorozirconates are weakly luminescing. Hexafluorozirconates M₂Zr(Hf)F₆ (M= K, Rb, Cs) and M₅Zr₄F₂₁ · 3H₂O (M = Rb, Cs), as well as oxofluorozirconate Rb₂Zr₃OF₁₂, are strongly luminescing compounds.