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.     

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*).     

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 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.     

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 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(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.     

Synthesis of rubidium fluorophosphatozirconates in the ZrO2-H3PO4-RbF-H2O system and their luminescent properties

Rubidium fluorophosphatozirconates (RFPZs) were synthesized along sections of the ZrO₂-H₃PO₄-RbF-H₂O system where PO ₄ ^3? /Zr = 1–2 (mol/mol) and RbF/Zr = 1–5 (mol/mol) and the initial solution contains 2–5 wt % ZrO₂. The following RFPZs have been isolated for the first time: RbZrF₂PO₄ · 0.5H₂O, Rb₃H₃Zr₃F₃(PO₄)₅, and RbZr₃F₄(PO₄)₃ · 1.5H₂O. Their formation fields were determined. The compounds were characterized using powder X-ray diffraction, crystal-optical analysis, chemical analysis, electron probe microanalysis, thermal analysis, and IR spectroscopy. Luminescent properties of the compounds were measured. All RFPZs are orthophosphates, have high thermal durability, and X-ray luminescence (XRL). Rb₃H₃Zr₃F₃(PO₄)₅ has the highest XRL intensity.     

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.     

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 complex cesium hydrosulfatophosphates

Solubility of the CsH₂PO₄-CsHSO₄-H₂O system has been studied using the isothermal method (25.0°C); the compounds Cs₄(HSO₄)₃(H₂PO₄), Cs₃(HSO₄)₂(H₂PO₄), and Cs₅(HSO₄)₂(H₂PO₄)₃ have been found to form; Cs₅(HSO₄)₂(H₂PO₄)₃ has been obtained for the first time. Single crystals of the isolated phases have been grown. Their composition has been determined, and agreement between the results of studying solid phases in the CsH₂PO₄-CsHSO₄-H₂O and these single-crystal samples has been demonstrated. X-ray diffraction analysis of these phases has been carried out.     

X-Ray Diffraction Study of Cs5(HSO4)3(H2PO4)2, a New Solid Acid with a Unique Hydrogen-Bond Network

Solid solution investigations in the CsHSO₄–CsH₂PO₄system, carried out as part of an ongoing effort to elucidate the relationship between proton conduction, hydrogen bonding, and phase transitions, yielded the new compound Cs₅(HSO₄)₃(H₂PO₄)₂. Single-crystal X-ray diffraction methods revealed that Cs₅(HSO₄)₃(H₂PO₄)₂crystallizes in space groupC2/c(or possiblyCc), has lattice parametersa=34.066(19) Å,b=7.661(4) Å,c=9.158(6) Å, andβ=90.44(6)°, a unit cell volume of 2389.9(24) ų, a density of 3.198 Mg m⁻³, and four formula units in the unit cell. Sixteen non-hydrogen atoms and five hydrogen sites were located in the asymmetric unit, the latter on the basis of geometric considerations rather than from Fourier difference maps. Refinement using anisotropic temperature factors for all non-hydrogen atoms and fixed isotropic temperature factors for all hydrogen atoms yielded residuals based onF²(weighted) andFvalues, respectively, of 0.0767 and 0.0340 for observed reflections [F²>2σ(F²)]. The structure contains layers of (CsH₂XO₄)₂that alternate with layers of (CsHXO₄)₃, whereXis P or S. The arrangement of Cs, H, andXO₄groups within the two types of layers is almost identical to that in the end-member compounds, CsH₂PO₄and CsHSO₄-II, respectively. Although P and S each reside on two of the threeXatom sites in Cs₅(HSO₄)₃(H₂PO₄)₂, the number of protons in the structure appears fixed. In addition, the correlation of S–O and S–OH bond distances with O···O distances, where the latter represents the distance between two hydrogen-bonded oxygen atoms, was determined from a review of literature data.     

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.     

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.     

Incorporation of cesium ion from CsNO3 into NH4Zr2(PO4)3 studied by TG-IR spectroscopy and powder XRD

The incorporation mechanism of Cs⁺ ions from CsNO₃ into NH₄Zr₂(PO₄)₃ was studied on a mixture of CsNO₃ and NH₄Zr₂(PO₄)₃ by powder X-ray diffraction analysis and by monitoring off-gases released from the mixture upon heating with a thermogravimetry analyzer connected to an infrared spectrometer. With increasing temperature, the decomposition of CsNO₃ first started, followed by the conversion of NH₄Zr₂(PO₄)₃ to HZr₂(PO₄)₃ with the release of NH₃. At around 500°C, the Cs Zr₂(PO₄)₃ phase started to appear as a result of the H⁺/Cs⁺ ion exchange. No Cs⁺ ion loss was observed at thermal treatment temperatures of 900°C and lower.     

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.     

Peroxofluorokomplexe der Übergangsmetalle. III,Darstellung, Kristallstruktur und Schwingungsspektren von K6Ta3(O2)3OF13 · H2O mit einem μ-Oxo-diperoxo-octafluoroditantalat(V)-Anion

Transition Metal Peroxofluoro Complexes. III. Preparation, Crystal Structure, and Vibrational Spectra of K₆Ta₃(O₂)₃OF₁₃ · H₂O Containing a m?-Oxo-diperoxo-octafluoroditantalate(V) Anion K₆Ta₃(O₂)₃OF₁₃ · H₂O has been prepared from solution and his crystal structure was determined by X-ray single crystal investigation: Space group Pnma, lattice constants a = 1 653.6 pm, b = 883.5 pm, c = 1 365.8 pm, Z = 4, R = 0.033. The compound yields [Ta(O₂)F₅]^2? groups as well as m?-oxo-bridged [Ta₂O(O₂)₂F₈]^4? anions with very diffrent O? O distances within the peroxo groups (139 pm vs. 164 and 175 pm) correlating well with the i.r. and Raman spectra. The different bonding in connection with an oxo-bridge is discussed.     

Crystal structure and proton conductivity of a new Cs3(H2PO4)(HPO4)·2H2O phase in the caesium di‐ and monohydrogen orthophosphate system

The M_x H_y (A O₄)_z acid salts (M = Cs, Rb, K, Na, Li, NH₄; A = S, Se, As, P) exhibit ferroelectric properties. The solid acids have low conductivity values and are of interest with regard to their thermal properties and proton conductivity. The crystal structure of caesium dihydrogen orthophosphate monohydrogen orthophosphate dihydrate, Cs₃(H_1.5PO₄)₂·2H₂O, has been solved. The compound crystallizes in the space group Pbca and forms a structure with strong hydrogen bonds connecting phosphate tetrahedra that agrees well with the IR spectra. The dehydration of Cs₃(H_1.5PO₄)₂·2H₂O with the loss of two water molecules occurs at 348–433 K. Anhydrous Cs₃(H_1.5PO₄)₂ is stable up to 548 K and is then converted completely into caesium pyrophosphate (Cs₄P₂O₇) and CsPO₃. Anhydrous Cs₃(H_1.5PO₄)₂ crystallizes in the monoclinic C 2 space group, with the unit‐cell parameters a = 11.1693 (4), b = 6.4682 (2), c = 7.7442 (3) Å and β = 71.822 (2)°. The conductivities of both compounds have been measured. In contrast to crystal hydrate Cs₃(H_1.5PO₄)₂·2H₂O, the dehydrated form has rather low conductivity values of ∼6 × 10⁻⁶–10⁻⁸ S cm⁻¹ at 373–493 K, with an activation energy of 0.91 eV.     

Heat Conductivity of Zirconium and Alkali Metal (Na,Cs) Phosphates of the NaZr2(PO4)3 Family

The heat conductivity of porous Zr₃(PO₄)₄, NaZr₂(PO₄)₃, CsZr₂(PO₄)₃, and Na₅Zr(PO₄)₃ samples was studied in the range 298-673 K. The heat conductivity coefficients of the zero-porosity phosphates under study were calculated and prospects for their application were considered.     

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.