Determination of amorphous layers on thick film Nasicon in dependence on different sintering processes

In thick film gas sensors Nasicon is used as a solid electrolyte with high Na⁺ ionic conductivity. Sensors like CO₂, O₂, Pt ▮ Na₂CO₃, BaCO₃ ∥ NASICON [Pt]_glass, O₂, CO₂ are suitable to measure the CO₂-concentration over 5 orders of magnitude. To characterize the screen printed Nasicon as a main component of such sensors grazing incidence diffractometry (GID), SEM, impedance spectroscopy and dc polarization measurements are performed in order to improve the long-term stability. The sintering process of the thick film influences the chemical surface composition of Nasicon and as a consequence the response of the sensor. Nasicon films sintered at temperatures between 1070 and 1210 °C show an amorphous layer increasing up to 1.1 μm thickness on the surface. Impedance measurements show, that cells using in such a way prearated Nasicon are responsible for water vapour. Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11 – 18 Sept. 1994     

Novel trivalent cation conducting solids and their application

Among the trivalent ion conductors reported, the highest ion conductivity was realized with the trivalent Al³⁺ ion conducting (Al_xZr_1−x)_4/(4−x)Nb(PO₄)₃ solid electrolyte and the value enters into the region between yttria stabilized zirconia (YSZ) and calcia stabilized zirconia (CSZ) that are well known to be high oxide anion conductors commercialized. The improvement of the ion conductivity and the mechanical strength was simultaneously achieved by adding B₂O₃ during the sintering procedure. The Al³⁺ ion conducting (Al_xZr_1−x)_4/(4−x)Nb(PO₄)₃ solid electrolyte with B₂O₃ treatment was combined with YSZ, and the 0.7La₂O₂SO₄-0.3Li₂SO₄ solid was attached on the (Al_xZr_1−x)_4/(4−x)Nb(PO₄)₃ solid surface as the auxiliary electrode for sulfur dioxide (SO₂) gas sensing. The sensor response was rapid, reproducible and continuous with obeying the Nernst theoretical relationship. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.     

Towards a thin films electrochromic device using NASICON electrolyte

The optimisation of the morphology of WO₃ thin films allowed a more efficient electrochromic colouring using Na⁺ ions than H⁺ ones. Therefore, sodium superionic conductor (Na₃Zr₂Si₂PO₁₂, NASICON) films may be used as electrolyte in inorganic electrochromic devices. In this paper, the structure, chemical composition, morphology and electrochromic properties of WO₃, ZnO:Al and Na₃Zr₂Si₂PO₁₂ thin films were studied to develop a novel type of electrochromic device. WO₃, ZnO:Al and Na₃Zr₂Si₂PO₁₂ thin films were deposited using reactive magnetron sputtering of tungsten, zinc and aluminium and Zr–Si and Na₃PO₄ targets, respectively. For transparent conductive oxide coatings, a correlation was established between the deposition parametres and the film’s structure, transmittance and electrical resistivity. Classical sputtering methods were not suitable for the deposition of NASICON films on large surface with homogenous composition. On the other hand, the use of high-frequency pulsed direct current generators allowed the deposition of amorphous films that crystallised after thermal annealing upon 700 °C in the Na₃Zr₂Si₂PO₁₂ structure. Amorphous films exhibited ionic conductivity close to 2 × 10⁻³ S cm⁻¹. Finally, preliminary results related to the electrochromic performance of NASICON, WO₃ and indium tin oxide devices were given. Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, France, Sept. 9–15, 2007.     

Preparation,proton transport properties and use in gas sensors of thin films of zirconium phosphate with γ-layered structure

Pellicular γ-zirconium phosphate (γ-ZP_(p)), i.e. sheets made up entirely of oriented lamellae of Zr(PO₄)(H₂PO₄)·2H₂O (γ-ZP), have been obtained by filtering colloidal dispersions of exfoliated γ-ZP in water/acetone. The ac-conductivity of γ-ZP_(p) and γ-ZP was measured in the temperature range 20/–20°C on samples previously conditioned at relative humidities between 90 and 5%. In both cases, the conductivity dependence on material hydration indicates the presence of a non-negligible bulk transport at low relative humidities. For each relative humidity the conductivity data have been parameterised on the basis of the Arrhenius equation. Activation energy and pre-exponential factor values suggest the presence of the same conduction mechanism in both materials. The conductivity of γ-ZP_(p) measured by applying the electric field parallel to the sheets ranges from 3·10⁻⁴ to 1·10⁻⁵ S cm⁻¹ for relative humidity decreasing from 90 to 11%, being an order of magnitude higher than that of γ-ZP. Since the pellicular and microcrystalline material have very similar surface areas (11–12 m²/g), the higher conductivity of γ-ZP_(p) is mainly due to the preferred particle orientation parallel to the electric field. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

Anion reorientation in anhydrous Na3PO4 during the phase transformation

The transport phenomena in alkali-metal super ionic conductors based on Na₃PO₄ structure are of particular interest due to their potential technological application. Differential thermal analysis (DTA), differential scanning calorimetry (DSC), Raman spectroscopy and temperature dependent electrical conductivity measurements were carried out to probe the nature of the phase transformation involved in anhydrous Na₃PO₄. The changes in spectral profile of the v₃ mode and the line width of v₁ mode of PO ₄ ³⁻ observed in the temperature interval from 331 to 345 °C revealed the high degree of disorder nature during the α-γNa₃PO₄ phase transformation. Paper presented at the 2nd Internation Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

D.C. conductivity of transparent conductive ZnO:Al films in the temperature range 80–360 K

An experimental study of the temperature dependence of the d.c. conductivity σ as a function of temperature T in the range from 80–360 K on nanocrystalline ZnO:Al films (Al³⁺ 2%) of thickness 500 nm prepared on glass microscope slides by a dip — coating method is presented. The electrical conductivity σ, which at room temperature varied between 0.1 to 2.7 S/cm, increased almost linearly with T for all the samples. Measurements of the Hall coefficient at room temperature and in a magnetic field of 1.2 T, gave R_H=0.53 cm³C⁻¹, from which a carrier concentration of n=1.18×10¹⁹ cm⁻³ and a carrier mobility of μ=1.40 cm²/Vs were deduced. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14–18, 2004.     

XRD, conductivity and FTIR studies on LiI-Li2WO4-Li3PO4 prepared by low temperature sintering

Different amounts of Li₃PO₄ were mixed to a fixed ratio of LiI:Li₂WO₄, ground and pelletised before subjected to sintering at 70°C for 7 days. XRD shows that the product formed after sintering process is most likely Li₆P₄W₈O₃₂ due to peaks present at 10.6°, 22.4°, 24.0°, 24.4, 26.2°, 32.4° and 34.0°. Conductivity studies show that the sample with 25 wt.% Li₃PO₄ exhibits the highest room temperature conductivity of 3.42×10⁻³ Scm⁻¹. Conductivity is expected to occur through channel-like structures which could have formed due to corner or edge sharing of polyhedra. FTIR studies have shown the existence of WO₄ tetrahedra and WO₆ octahedral at 850 cm⁻¹ and 952 cm⁻¹, and phosphate tetrahedral at 564 cm⁻¹, 700 cm⁻¹, 890 cm⁻¹ and 1030 cm⁻¹.     

Anharmonic force constants of GaSb from the measured third order elastic constants at 300°K

The third-order elastic constants of single crystal GaSb are determined using ultrasonic pulse interferometer at 10 MHz. The constants at 300°K, in units of 10¹¹ N.m.⁻², are C_l11 = ™ 4 ·75 ± 0·06 C₁₄₄ = + 0·50 ± 0·25 C₁₁₃ = ™ 3 ·08 ± 0·02 C₁₆₆ = ™ 2·16 ± 0·13 C₁₂₃ = ™ 0 ·44 ± 0·29 C₄₅₆ = ™ 0·25 ± 0·15 These constants are used to evaluate the three anharmonic first and second neighbour force constants based on modified Keating’s model. The constants are (in units of 10¹¹ N.m⁻²)γ=− 2·406;δ=0·407;ε=−0·222.     

快离子导体中的钠沉积

采用电子探针(EPMA)定点轰击法研究了β-,β″-Al₂O₃和Nasicon(Na₃Zr₂Si₂PO₁₂)的钠沉积效应。按照递减离子源的离子迁移和电解沉积机理导出了钠沉积动力学方程式,可以较好地说明快离子导体在电子束轰击下钠计数率随时间的变化。在β-Al₂O₃单晶内有丰富的可迁移钠离子源,曲线上升的延续时间较长;而对于Na_关键词：     

Solvothermal synthesis of LiCo<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript>/C cathode materials for lithium-ion batteries

LiCo_1−x Mn _x PO₄/C cathode materials are selectively synthesized by a solvothermal method in ethylene glycol solvent using glucose, LiCl, H₃PO₄, MnCl₂·4H₂O, and Co(NO₃)₂·6H₂O as precursors. The obtained samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) and the electrochemical performances are also evaluated using a LAND CT2001A battery test system at room temperature. XRD result demonstrates the formation of LiCo_1−x Mn _x PO₄ solid solution and the enlarged channels are benefit for Li⁺ migration. SEM graph indicates that the particle size of LiCo_0.5Mn_0.5PO₄/C is about several hundred nanometers and aggregates to large particles located in the range of 2–3 μm. TEM image illustrates that the core/shell-structured LiCo_0.5Mn_0.5PO₄/C solid solution is indeed obtained by this method. The high specific surface area (35 m²/g) of LiCo_0.5Mn_0.5PO₄/C could make this solid solution contact with the electrolyte more sufficiently and benefit for Li⁺ transportation. The capacity, flat voltage, and cyclical stability of LiCo_1−x Mn _x PO₄/C are improved compared to LiMnPO₄ and LiCoPO₄ due to the improved electronic conductivity and lithium-ion conductivity which resulted from carbon coating and foreign element incorporation.     

The vibrational spectra and structural properties of Me7Eu2UO2(PO4)5 crystals

We investigate the vibrational spectra of crystals of ternary orthophosphates Me₇Eu₂UO₂·(PO₄)₅ (Me–Na, Rb, Cs) obtained by solid-phase synthesis. We show that in these materials the effect of coordination distorts the geometry of the PO ₄ ³⁻ tetrahedron and decreases its symmetry. We conclude that the PO ₄ ³⁻ tetrahedrons in Me₇Eu₂UO₂(PO₄)₅ occupy two nonequivalent positions in the lattice. The character of manifestation and the number of oscillation frequencies observed allow the assumption that they have the C_3v- and C₂-symmetry. This symmetry of two crystallographically nonequivalent groups of PO ₄ ³⁻ ensures a complete set of bands in the IR absorption spectra of the crystals investigated. We show that these crystals exhibit chain structural motifs. Translated from Zhurnal Prikladnoi Spektroskopii, Vol, 64, No. 4, pp. 467–470, July–August, 1997.     

Thin porous anodic alumina films: Interface trap density determination

The electrical properties of thin porous alumina films in the form of MOS structures were studied with dielectric spectroscopy at room temperature. The thickness of the samples was found to be approximately 95 nm with a cross section area of 1.6×10⁻³ cm².C-V andG-V measurements were performed by applying a loop sweep voltage 2.0 V to −5.0 V. Correction to the measurements were performed by considering a series resistanceR _S and leakage currentI _DC. TheC-V results show hysteresis effects due to the presence of positive charges in porous alumina. These charges may be are attributed to the residual electrolyte during the anodization process in the sample preparation. Three distinct regions in theC-V results are observed, namely the inversion, the depletion and the accumulation regions. In the voltage region, where depletion of carriers is observed,C-f andG-f measurements were recorded in the frequency range 1 Hz to 10⁶ Hz. The conductance method was applied for the calculation of the density D_it of carriers, trapped in the interface between insulator and semiconductor, and of the response time τ_it as a function of the applied bias voltage were performed. The values obtained for D_it and τ_it are of the order of 3×10¹² eV⁻¹ cm⁻² and 10⁻³ s, respectively, and they are voltage dependent. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.     

Polarisation resistance of the O2, Au/O2− and H2-H2O, Au/O2− electrode systems

Gold electrodes with known contact geometries were studied using impedance spectroscopy. From these data it was possible to determine the specific polarisation conductivity per unit length of three-phase boundary (TPB). The values were found to be (3÷22)×10⁻⁴ S·cm⁻¹ dependent on the electrode history in pure oxygen at 977 °C and 2×10⁻⁶ S·cm⁻¹ at 977 °C in “pure” hydrogen (P_O2=10⁻²⁰ atm at 1001 °C). The results are compared with previous data obtained for platinum electrodes.     

Atmospheric gamma rays in the energy region 40–1000 GeV

A large stack of lead-emulsion sandwich detector assembly was flown over Hyderabad, India. High energy gamma rays at the float altitude were unambiguously identified from the cascades they induced, and their energies reliably determined by improved methods. From an analysis of 163 gamma rays of energy ≳ 30 GeV, it is found that the differential energy spectrum is represented by the power lawJ _r (E)= 129·4E ^{−2·62±0·12} photons m⁻² sr⁻¹sec⁻¹ GeV⁻¹ at an effective atmospheric depth of 14·3 g cm⁻²; this is the first reliable balloon measurement of atmospheric gamma rays in the energy range 40–1000 GeV. After correcting for the gamma rays radiated by the primary cosmic ray electrons, the production spectrum of gamma rays, resulting from the collisions of cosmic ray nuclei with air nuclei, at the top of the atmosphere isP _r (E, 0)=8·2 × 10⁻⁴ E^2.60±0.09 photons g⁻¹sr⁻¹sec⁻¹ GeV⁻¹. The atmospheric propagation of the electromagnetic component due to the cascade process is also derived from the gamma ray production spectrum.     

The local structure and interactions between V4+ ions in soda-phosphate glasses

EPR investigation on xV₂O₅ · (100 −x)[2P₂O₅ · Na₂O] and xV₂O₅ · (100 −x)[P₂O₅ · mNa₂O] (m = 1.5 and 2) glass systems was performed. The changes observed in the EPR spectra of xV₂O₅× (100 −x)[2P₂O₅ · Na₂O] glasses with increasing content of vanadium oxide are explained supposing that these spectra consist of two superposed EPR signals, one with hyperfine structure typical for isolated ions and another one consisting of a broad line without hyperfine structure characteristic for clustered ions. The clustered V⁴⁺ ions are not evidenced at low V₂O₅ contents (x = 5 mol%). The EPR spectra of xV₂O₅ · (100 −x)[P₂O₅ · mNa₂O] glasses indicate a superposition of two or three hyperfine structures attributed to nonequivalent VO²⁺ centers. Spin Hamiltonian parameters (g, A), dipolar hyperfine coupling parameter (P) and Fermi contact interaction term (K) have been evaluated. The ratio between the number of clustered and isolated ions was also determined.     

X-ray determination of thermal expansion of cadmium fluoride and lead fluoride

The lattice parameters of CdF₂ andβ-PbF₂ have been determined over the temperature range 300–670 K. The coefficient of expansion at room temperature is 21·3 × 10⁻⁶ K⁻¹ and 25·4 × 10⁻⁶ K⁻¹ for CdF₂ and PbF₂ respectively and it increases linearly with temperature over the range of temperature covered. The Grüneisen parameter decreases with temperature in both the crystals.     

The temperature and light intensity dependence of photorefraction in LiNbO3

In the paper the dependence of the photorefraction (PhR) in LiNbO₃ and LiNbO₃−Fe (0.1 wt%, 0.3wt%) crystals on light intensity (within 10¹⁶–10²³ quanta·cm⁻²·s⁻¹ at wavelengths 496.5 nm and 600 nm) and temperature (in the region 100–500 K) is studied. For all the crystals the limiting values of PhR are similar and atT=293 K Δn _sat ^lim ≈3·10⁻³. In LiNbO₃ the temperature dependence of PhR in the range 100–500 K requires to take into account at least two trapping centres.     

The effect of LaPO4 in the LixLa2/3Ti1−xPxO3+x system

Lithium ion conductors of the overall composition Li_xLa_2/3Ti_1−xP_xO_3+x (hereafter referred to as LTP) based on La_2/3TiO₃ were prepared by solid state reaction at high temperature (1300 °C). AC impedance measurements indicate that the total conductivities are of the order of 10⁻⁴ S·cm⁻¹ when x=0.28 − 0.35 at room temperature and have an activation energy of 18 kJ·mol⁻¹ in the temperature range from room temperature to 400 °C. X-ray powder diffraction patterns showed that the LTP system has a complex composition, which contains the solid solution perovskite Li_3xLa_2/3−xTiO₃ and LaPO₄.     

Highly Selective Fluorescent Recognition of Pyrophosphate in Water by a New Chemosensing Ensemble

A new chemosensing ensemble that displays sensitive and selective fluorescent recognition of pyrophosphate in water at pH 7.4 has been developed. The ensemble is constructed by a copper complex (receptor) and eosin Y (indicator), the constructed ensemble is capable of highly selectively discriminate pyrophosphate from other common existing anions such as CH₃COO⁻, HSO₄⁻, NO₃⁻, H₂PO₄⁻, HPO₄²⁻, PO₄³⁻, NCS⁻, I⁻, Cl⁻, Br⁻, F⁻as well as some structurally similar carboxylates such as citrate, tartrate, oxalate, malonate, succinate and glutarate.     

EPR of Fe3+ ion and symmetry of [AIF5·H2O]2? complex ion in (NH4)2AIF5·H2O single crystals

We used the spin-Hamiltonian method for the analysis of the electron paramagnetic resonance (EPR) spectrum of Fe³⁺ as a probe ion in (NH₄)₂AlF₅·H₂O single crystalline basic material. The theoretical expressions for the magnetic field (at which the fine structure transition lines appear) versus the angle between the magnetic field and the axis of symmetry of the magnetic complex are also given. These values were calculated by applying the perturbation theory to the second-order terms. From the experimental results (at 300 K and 9.21 GHz), the spin-Hamiltonian parameters were deduced:D=(668±10)·10⁻⁴ T,E=(−56±10)·10⁻⁴ T,a=(−54±10)·10⁻⁴ T,F=(30±10)·10⁻⁴ T. An isotropic superhyperfine structure was evidenced for the five fluorine ions. The obtained EPR data were used to determine the local symmetry of the Al³⁺ ion. A good agreement with X-ray diffraction measurements was found.