A series of new zirconium and titanium phosphates-organophosphonates, in which the organophosphonate moiety is functionalized with a sulfo group, was prepared by a topotactic reaction involving the gamma modification of zirconium or titanium hydrogen phosphate with 2-bis(phosphonomethyl)amino-ethan-1-sulfonic acid (H4TDP). H4TDP represents a new type of functionalizing agent, which can be easily prepared by a Moedritzer-Irani reaction from taurine (2-aminoethanesulfonic acid). The gamma modification of zirconium hydrogen phosphate (γ-ZrP) with H4TDP provides mixed phosphate-organophosphonate compounds with the formula Zr(PO4)(H2PO4)1-2x(H2TDP)x·yH2O, where x = 0.15, 0.34, 0.45, and is controlled by the γ-ZrP/H4TDP ratio in the starting mixture. On the contrary, by the topotactic gamma modification of titanium hydrogen phosphate (γ-TiP) with H4TDP, only one product with the formula Ti(PO4)(H2PO4)1-2z(H2TDP)z·yH2O, where z = 0.41 ± 0.01, was obtained regardless of the composition of the starting mixture. The synthesized compounds were characterized by elemental analysis, thermogravimetric analysis, energy-dispersive X-ray analysis, and infrared spectroscopy. The way the topotactic reaction proceeds and how the grafted organophosphonate groups are bonded to the layers of the host structure were suggested on the basis of the solid-state NMR data. It was found that the grafted moieties are spread evenly in the host layers among the hydrogen phosphate groups. The obtained solids are able to intercalate basic molecules, as was proved by the intercalation reactions of the zirconium series with butylamine. The amount of intercalated butylamine increases with increasing x. It is known that both host compounds, γ-ZrP and γ-TiP, are protonic conductors. It was found that the incorporation of H2TDP increases conductivity of the zirconium compound when x = 0.15, but further incorporation of H2TDP into the γ-ZrP host structure leads to a decrease of conductivity. This behavior is explained on the basis of the 1H MAS and the 1H-1H EXSY NMR data.

Cerium(IV) phenylphosphonates and 4-substituted phenylphosphonates were prepared by reaction of a cerium(IV) salt with corresponding acids (phenylphosphonic, 4-carboxyphenylphosphonic, 4-sulfamoylphenylphosphonic, 1,4-benzenediphosphonic, 1,4-biphenyldiphosphonic and 4-sulfophenylphosphonic acid) and characterized by elemental analysis, energy-dispersive X-ray analysis, TGA, powder X-ray diffraction and infrared spectroscopy. Three different cerium phenylphosphonates can be prepared in dependence on the reaction conditions. On the other hand, only one compound is formed in each 4-substituted phosphonate system regardless the variation of the reaction conditions. All three phenylphosphonates, 4-carboxyphenylphosphonate and 4-sulfamoylphenylphosphonate are layered with the organic parts pointed below and above the plane of the metal phosphonate layers, with the functional groups placed at the end of the organic part. 4-Sulfophenylphosphonate, 1,4-benzenediphosphonate and 4,4′-biphenyldiphosphonate form pillared structures. Cerium 4-carboxyphenylphosphonate is able to intercalate aliphatic amines due to the presence of the free carboxylic groups in its interlayer space.

The resistive random access memory is promising to replace the traditional memory technology and the buffer layer plays an important role in chalcogenide based electrolytes. However, there is still lack of convincing experimental result regarding with the mechanism of buffer layer. In this letter, two sets of devices were designed with different position of buffer layer, which proves the buffer layer facilitates the nucleation of Ag filaments.

The dependence of impedance spectra on temperature and sample thickness are analyzed for AgAsS2 as a case example. Using the scaling properties of complex conductivity with thickness and temperature, we discuss the bulk and interfacial properties of the materials. Important physical parameters such as the number of mobile ions, diffusion coefficient in the bulk, and interface are deduced. The influence of the thickness of the sample on conductivity behavior is also discussed. A significant electrode polarization effect is observed even for a low number of localized (accumulated) ions (≈2 × 1017 cm−3) near the interface, which is significantly lower than the number of mobile ions (≈8 × 1021 cm−3) in this test material. The presented analytical method can be widely applied to potentially important ionic conducting systems.

Conventional analysis of data recorded using the Electrochemical Impedance Spectroscopy (EIS) is a relatively simple procedure from the mathematical point of view. It involves an elucidation of electrode processes to derive their characteristic parameters. Another advantage is that it represents a quick visualization tool being still a very sensitive technique [1,2]. However, it has a number of disadvantages too. Often, the interpretation of EIS data using equivalent circuits is quite difficult due to a tedious search for a good fitting correlation. Moreover, results do not give information about number of moving ions (cations or anions), hopping time etc. Knowledge and consideration of these parameters would be very helpful in many electrochemistry-related fields, such as for instance in the development of solid state batteries and in the semiconductor field. Being unhappy with these drawbacks and limitations of the conventional data analysis method, we recently developed a new approach [4] in which the Z 1 - Z 2 complex impedance plane (where Z 1 and Z 2are the real and imaginary parts of the impedance of materials) has been analyzed, based on Dyre’s random-walk theory. Through this approach we have obtained from EIS data (that are measured anyway), a new set of physical parameters, yet unseen and unmined: i) the diffusion coefficient D and ii) the number of moving ions N ions, both parameters further distinguishable in the bulk region of the sample as well as at the interface. The presentation will explain in detail our recently developed approach that has the potential to find a widespread use in various electrochemical fields, such as in batteries, solar cells, fuel cells and semiconductor industry in general. The presentation will show, how helpful this approach can be to understand the electrode polarization as well as the ionic transport mechanism in various conductors. In particular, we will discuss in detail recent results achieved on various materials, including selected ionic conductors [3-5], silicons and titanium dioxides [6]. Literature: D. D. Macdonald, Transient Techniques in Electrochemistry, Springer US, 1977. E. Barsoukov, J. R. Macdonald, Impedance Spectroscopy Theory, Experiment, and Application, Second Ed., John Wiley and Sons, New Jersey, 2005 S. Stehlik, J. Orava, T. Kohoutek, T. Wagner, M. Frumar, V. Zima, T. Hara, Y. Matsui, K. Ueda, M. Pumera, J. of Solid State Chem. 183 (2010) 144. S. Stehlik, K. Shimakawa, T. Wagner and M. Frumar, J. Phys. D: Appl. Phys. 45(2012) 205304. D.S. Patik, K. Shimakawa, V. Zima, J. Macak, and T. Wagner, J. Appl. Phys. 113 (2013) 143705. T.Wagner et al., Ms in preparation.

Analysis of impedance spectra by a random-walk approach is proposed for the study of ionic-transport materials with a silver-containing chalcogenide glass as a case example. Through a full analysis of complex impedance spectra including the electrode polarization effect, some important physical parameters, such as the number of mobile ions in bulk and interface regions, the diffusion coefficient, etc., are extracted without using the conventional equivalent electric circuit analysis. A detailed discussion on electrode polarization, which is highly dependent on signal amplitude, is also presented.

New functionalized layered titanium phenylphosphonates were prepared by reactions of titanium(IV) tetraisopropoxide with corresponding phosphonic acids (phenylphosphonic, 4-carboxyphenylphosphonic, 4-sulfamoylphenylphosphonic, 1,4-benzenediphosphonic and 4-sulfophenylphosphonic acid) and subsequent hydrothermal or solvothermal treatments at 180°C for 60h. The compounds prepared were characterized by EDX, elemental analysis, TGA and powder X-ray diffraction. The ability of the compounds prepared to intercalate basic compounds was tested using aliphatic amines and diamines.

A series of metal coordination polymers, [Li-2(OBA)] (1), [Na-2(OBA)(H2O)] (2), [K(HOBA)] (3), [Rb(HOBA)] (4), [Cs(HOBA)] (5), [Mg(OBA)(H2O)(2)] (6), [Ca(OBA)(H2O)] (7), and [Sr(OBA)(H2O)] (8) (H(2)OBA = 4,4'-oxybisbenzoic acid), was synthesized from alkali and alkaline-earth metal salts and 4,4'-oxybisbenzoic acid by solvothermal reactions. Single crystal X-ray structure analysis revealed that compounds 1-5 and 7-8 are three-dimensional while complex 6 has a layered structure. The inorganic motifs, ranging from discrete octahedra (6), edge-sharing octahedral dimers (7), and straight one-dimensional inorganic chains (1 and 8) to two-dimensional inorganic layers (2-5), are connected through organic linkers and thus form neutral networks. High thermal stabilities were observed for compounds 1, 2, 6, 7, and 8 up to approximately 500 degrees C. Electrochemical measurements of 1 revealed a stabilized reversible capacity of approximately 100 mAh g(-1) after more than 30 charge/discharge cycles.

The electric properties of LiI containing chalcohalide glasses in the system Ga2S3–GeS2 were studied by means of impedance spectroscopy and potentiostatic chronoamperometry. Two sets of the samples were prepared by direct synthesis from elements and compounds in evacuated quartz ampoules. The prepared glasses were as follows: xLiI–xGa2S3–(100−2x)GeS2, x=15, 20, 25 and 20LiI–xGa2S3–(80−x)GeS2, x=0, 5, 10, 15 and 20. In the first set the concentration of LiI increased and the second set was prepared to study the influence of Ga2S3 on the properties of the glasses. Additional aim of this work was to compare the electric properties of LiI containing Ga2S3–GeS2 glasses with analogous AgI containing Ga2S3–GeS2 glasses recently studied by us. The conductivity of the LiI containing glasses in the Ga2S3–GeS2 system was higher and the activation energy was lower than in the analogous AgI containing system. The residual electronic (hole) conductivity remained similar in both systems being almost negligibly low. Raman spectroscopy proved the influence of LiI as well as Ga2S3 on glass structure, however interpretation of Raman spectra of these glasses is complicated due to small mass difference between gallium and germanium.

We report on electric properties of Agx(As0.33Ch0.67)100−x (Ch═S, Se, Te) glass systems in relation to their microstructure and changing constituting chalcogenide atoms. We observed decreasing contribution of the ionic conductivity when sulphur was replaced by selenium and tellurium. We also found a strong correlation between the conductivity and the phase separation into a silver-rich and a silver-poor phase which appears to be responsible for the semiconductor — ionic conductor transition in the sulphur and selenium based systems.

Intercalates of calcium phenylphosphonate dihydrate with 1-alkylamines (C2–C10), 1-alkanols (C3–C10), 1,ω-amino alcohols (C2–C5), pyridine, morpholine, piperazine, aniline and 1-naphthylamine were prepared and characterized by powder X-ray diffraction and thermogravimetric analysis. The intercalates of alkanols and alkylamines are unstable at ambient conditions and the guest molecules are tilted to the host layers at an angle of 40°. The amino alcohol intercalates are stable and their basal spacings are very similar for all amino alcohols used and, in the case of ethanolamine and propanolamine, they contain co-intercalated water. Also arylamines and nitrogenous heterocycles form stable compounds. The general formula of these intercalates is CaC6H5PO3·xH2O·y(guest) and their basal spacings are from 15.39 to 15.78 Å.

The dependence of basal spacing and water content of BaC6H5PO3·xH2O on the relative humidity was studied. Intercalates of 1-alkylamines (C2–C10) and 1-alkanols (C3–C10) were prepared from barium phenylphosphonate dihydrate and also from anhydrous host and characterized by powder X-ray diffraction and thermogravimetric analysis. The intercalates of alkanols and alkylamines prepared from dihydrate are quite stable at ambient conditions and contain one guest molecule per formula unit. The guest molecules are probably arranged in monomolecular way and are perpendicular to the host layers in the case of amines or tilted to the host layers at an angle of about 80° in the case of alkanols. The intercalates prepared from anhydrous host are unstable and their basal spacings indicate parallel arrangement of the guests chains. Formation of mixed intercalates was not observed when barium phenylphosphonate dihydrate was contacted with a mixture of alkanols or amines.

Glasses with general formula Agx(As0.33Se0.67)100−x were studied by means of modulated differential scanning calorimetry (MDSC), conductivity and permittivity measurements and atomic force acoustic microscopy (AFAM). In the whole range of doping (x=2–12at.% Ag) a phase separation was supposed. The proportional amount of the ion-conductive Ag rich phase increased with the Ag content. A rapid increase (almost four orders of magnitude) in the conductivity was observed in the Ag concentration range 4–8at.%, which could be associated with the interconnection of this ion-conductive phase. The transition from a hole conductivity (at low Ag concentration) to a mixed ionic-hole conductivity at higher Ag concentration was studied by permittivity measurements.

New barium phenylphosphonate dihydrate—BaC6H5PO3·2H2O—was prepared by precipitation from barium salt and phenylphosphonic acid solutions with pH adjusted to 8.5. The compound was characterized by powder X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray analysis and infrared spectroscopy. It was found that this compound reacts with phenylphosphonic acid to form previously described barium hydrogen phenylphosphonate—Ba(C6H5PO3H)2. This reaction also proceeds in an opposite direction, i.e., Ba(C6H5PO3H)2 reacts with Ba2+ in diluted ammonia to produce BaC6H5PO3·2H2O. Infrared spectra of both barium compounds are described and compared with those of analogous strontium compounds and phenylphosphonic acid. Preliminary intercalation experiments indicated that BaC6H5PO3·2H2O could be a promising host material for intercalation of amines.

Electrical properties of (100-2x)GeS(2-x)Ga(2)S(3-x)Agl (x=15, 20, 25, 30 at.%), 60GeS(2)-20Ga(2)S(3)-20AgX (X = Cl, Br and I) and (60GeS(2)-20Ga(2)S(3)-20Agl)(100-x)-Ag-x (x=1 and 5 at.%) chalcohalide glasses are described in terms of conductivity and permittivity. The impedance spectroscopy method was used in the frequency range of 0.1 to 10(6) Flz and in the temperature range of 258 to 393 K for our conductivity and permittivity studies. We observed all Arrhenius behavior for all samples in the case of the temperature dependence of conductivity and a large dispersion of the real part of permittivity with decreasing frequency was identified. We also found a power-law dependence of the conductivity oil the silver iodide content and an unusual almost linear dependence of the exponent alpha on the temperature. In addition, we determined frequencies f(ip) which were found to be threshold frequencies between the polarization due to the space charge accumulation and a rapid polarization process Occurring in glassy ionic conductors. (C) 2008 Elsevier B.V. All rights reserved.

In this paper, bulk glasses with composition Agx(As33S67)100−x (x=0–25at.%) were investigated. Amorphous structure of samples was confirmed by X-ray diffraction analysis. The structure was deduced from Raman spectra measured for all silver contents in the As–S matrix. The thermal properties (Tg – glass-transition temperature, Ts – softening temperature, Tc – temperature of crystallization, Tm – melting temperature and Cp – specific heat capacity), were obtained from modulated differential scanning calorimetry (MDSC) and/or thermomechanical analysis (TMA). Optical properties were measured by spectral ellipsometric spectroscopy. Refractive indices were calculated using the Cauchy model from the ellipsometric parameters Ψ, Δ. Refractive index increasing toward higher silver concentration has been shown. The value of the refractive index difference (Δn) between As33S67 and Ag25(As33S67)75 is about 0.4. All studied glasses behave as ionic conductors from the point of their electrical properties. Their ac conductivity increases with increasing content of silver. As determined from the comparison of ac and dc conductivities, the contribution of electronic conductivity to the overall conductivity is very low and decreases from about 1% for the glass with 10at.% of Ag to about 0.01% for the glass with 24at.% of Ag.

The selective oxidation of 5-hydroxymethyl-2-furaldehyde (HMF) to furan-2,5-dicarboxaldehyde (FDA) has been studied under different conditions, in terms of reaction temperature, oxidant agent (air, oxygen and their pressure), type of solvent (water, organic), in the presence of heterogeneous catalysts based on VOPO4·2H2O (VOP). The attempt of obtaining in a one-pot reaction FDA from fructose passing through HMF as an intermediate product failed both in water and in a mixed water/methyl isobutyl ketone (MIBK) medium. The best performances in the direct oxidation of HMF to FDA have been obtained when VOP and N,N-dimethylformamide (DMF) were used as a heterogeneous catalyst and a reaction medium, respectively, under mild conditions (100°C and room pressure of O2). Productivity up to 8.13mmol of FDA/(g catalysth) was achieved with 95% selectivity at low HMF conversion. The modification of the heterogeneous catalysts, obtained by partial substitution of VO3+ with different metal cations (Fe3+, Cr3+, Ga3+, Mg2+, Cu2+ and Pd2+), did not cause any improvement on the performances in this reaction.

Layered compounds with the general formula MOXO4·yH2O (M=V, Nb; X=P, As) were prepared. The content of water y was controlled by keeping the samples in an atmosphere with various relative humidities (RH). Depending on RH, the formation of several hydrates of niobyl phosphate and arsenate was observed and their basal spacings (d) were determined, namely, NbOPO4·H2O, d=6.4Å, at 11% RH and lower, NbOPO4·2H2O, d=7.0Å, at 22–33% RH, NbOPO4·3H2O, d=7.8Å, at 43–84% RH, and NbOPO4·5H2O, d=8.0Å, at 92% RH and above; NbOAsO4·H2O, d=6.2Å, at 0–16% RH and NbOAsO4·3H2O, d=7.9Å at 33% RH and above. As follows from ac and dc conductivity data, NbOXO4·yH2O compounds are practically pure protonic conductors, whereas VOXO4·yH2O compounds are mixed protonic–electronic conductors and the protonic component increases with y. Two intercalates of MOXO4·yH2O with inorganic acids were prepared. A new intercalate of H3AsO4 into VOAsO4·yH2O with the formula VOAsO4·0.5H3AsO4·yH2O (y=0.5–0.8) has the cell parameters a=6.37 and c=8.81–9.13Å at 0–22% RH. Above 22% RH, the intercalate decomposes and the parent VOAsO4·yH2O with H3AsO4 adsorbed on the surface is formed. Another intercalate with formula NbOPO4·H3PO4·yH2O (y=2–4 at 0–75% RH) has the cell parameters a=6.43 and c=9.56–9.70Å at RH from 0% to 5% and a=6.48 and c=11.2Å at RH from 33% to 75%. Both intercalates are more conductive than their MOXO4·yH2O hosts and their conductivity increases with increasing RH of the surrounding atmosphere. Like NbOPO4·yH2O, also NbOPO4·H3PO4·yH2O can be considered pure proton conductor and its conductivity at 20°C reaches 5×10−3Scm−1 for y=4.

Three new calcium phenylphosphonates, CaC6H5PO3-2H(2)O, Ca-3(C6H5PO3H)(2)(C6H5PO3)(2)(.)4H(2)O, and CaC6H5PO3. H2O, and two calcium 4-carboxyphenylphosphonates, Ca(HOOCC6H4PO3H)2 and Ca-3(OOCC6H4PO3)(2)(.)6H(2)O, were prepared. It was found that CaC6H5PO3-2H2O transformed into previously known Ca(C6H5PO3H)(2) via Ca-3(C6H5PO3H)(2)(C(6)H5PO(3))(2)(.)4H(2)O in the presence of phenylphosphonic acid, and vice versa, Ca(C6H5PO3H)(2) turned into CaC(6)H(5)PO(3)(.)2H(2)O in a weak basic medium. A similar relationship was found between Ca(HOOCC6H4PO3H)(2) and Ca-3(OOCC6H4PO3)(2)(.)6H(2)O; i.e., Ca-3(OOCC6H4PO3)2(.)6H(2)O transformed into Ca(HOOCC6H4PO3H)(2) in the presence of 4-carboxyphenylphosphonic acid. On the contrary, Ca-3(OOCC6H4PO3)2(.)6H(2)O is formed from Ca(HOOCC6H4PO3H)(2) in the presence of ammonium as a weak base. The structure of Ca(HOOCC6H4PO3H)(2) was solved from X-ray powder diffraction data by an ab initio method using a FOX program. The compound is monoclinic, space group C21c (No, 15), a = 49,218(3) angstrom, b = 7.7609(4) angstrom, c = 5.4452(3) angstrom, beta = 128.119(3)degrees, and Z = 4. Its structure is one-dimensional with [Ca-2(HOOCC6H4PO3H)(4)](infinity) ribbons forming basic building blocks. The ribbons are held together by hydrogen bonds between carboxylic groups.

Intercalation compounds of vanadyl phosphate with cyclic ketones (cyclopentanone, cyclohexanone, 4-methylcyclohexanone, and 1,4-cyclohexanedione) were prepared from corresponding propanol or ethanol intercalates by a molecular exchange. The intercalates prepared were characterized using powder X-ray diffraction and thermogravimetric analysis. The intercalates are stable in dry environment and decompose slowly in humid air. Infrared and Raman spectra indicate that carbonyl oxygens of the guest molecules are coordinated to the vanadium atoms of the host layers. The local structure and interactions in the cyclopentanone intercalate have been suggested on the basis of quantum chemical calculations.