A comparative study of Keane''s and Stacey''s equations of state

Chitosan acetate-ammonium nitrate (NH₄NO₃) films have been prepared by the solution-cast technique. Fourier transform infrared spectroscopy (FTIR) showed that complexation has occurred. FTIR exhibited shifts in amine and carbonyl bands from 1553 to 1520 cm⁻¹ and 1636 to 1617 cm⁻¹. A new peak was also observed at 1746 cm⁻¹. XRD shows that all complexes are amorphous. The highest conductivity at room temperature is 2.53×10⁻⁵ S cm⁻¹ for the film containing 45 wt% NH₄NO₃. The conductivity of the samples is dependent on the number of mobile ions and mobility.     

Sonochemical synthesis,characterization, thermal and semiconducting behavior of nano-sized azidopentaamminecobalt(III) complexes containing anion,CrO42− or Cr2O72−

New nano-sized cobalt(III) coordination complexes, [Co(NH₃)₅N₃]CrO₄ (1N) and [Co(NH₃)₅N₃]Cr₂O₇ (2N) were synthesized using an innovative sonochemical methodology based on reaction between [Co(NH₃)₅N₃]Cl₂ and potassium salt of CrO₄²⁻ or Cr₂O₇²⁻ in aqueous medium. These complexes were also compared with their respective bulks which were synthesized under identical conditions in the absence of sonicaion. All the complexes were characterized by elemental analysis and spectroscopic techniques (UV–visible and IR). Morphology and particle size of nano-sized complexes was determined by SEM and Zeta-sizer respectively. TGA was used for comparative thermal stability and XRD to identify the phase difference between nano structures and bulk complexes. Furthermore, the electrical property was investigated and all complexes were found to be electrical semiconducting materials and 2N shows better result than others. The single crystals X-ray structure study of new [Co(NH₃)₅N₃]Cr₂O₇ revealed the presence of discrete ions, [Co(NH₃)₅N₃]²⁺ and Cr₂O₇²⁻, crystallizes in monoclinic, space group P_c, with R = 0.0636 in the solid state.     

Preparation of LSGM powders for low temperature sintering

La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 powders were prepared by carbonate coprecipitation and the tuning of the cation composition by a solid state reaction. The relative compositions of La, Sr, Ga, and Mg were dependent upon the supersaturation ratio (R = [(NH₄)₂CO₃]/([La³⁺] + [Sr²⁺] + [Ga³⁺] + [Mg²⁺])) during the coprecipitation. The coprecipitation of a Sr-deficient source solution and the subsequent replenishment of SrO and MgO by ball milling were effective for accomplishing a phase-pure La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 specimen by low-temperature sintering.     

1H NMR study of proton dynamics in (NH4)3H(SO4)2

Proton dynamics in (NH₄)₃H(SO₄)₂ has been studied by means of ¹H solid-state NMR. The ¹H magic-angle-spinning (MAS) NMR spectra were traced at room temperature (RT) and at Larmor frequency of 400.13 MHz. ¹H static NMR spectra were measured at 200.13 MHz in the range of 135–490 K. ¹H spin-lattice relaxation times, T₁, were measured at 200.13 and 19.65 MHz in the ranges of 135–490 and 153–456 K, respectively. The ¹H chemical shift for the acidic proton (14.7 ppm) indicates strong hydrogen bonds. In phase III, NH₄⁺ reorientation takes place; one type of NH₄⁺ ions reorients with an activation energy (E_a) of 14 kJ mol^− 1 and the inverse of a frequency factor (τ₀) of 0.85 × 10^− 14 s. In phase II, a very fast local and anisotropic motion of the acidic protons takes place. NH₄⁺ ions start to diffuse translationally, and no proton exchange is observed between NH₄⁺ ions and the acidic protons. In phase I, both NH₄⁺ ions and the acidic protons diffuse translationally. The acidic protons diffuse with parameters of E_a = 27 kJ mol^− 1 and τ₀ = 4.2 × 10^− 13 s. The translational diffusion of the acidic protons is responsible for the macroscopic proton conductivity, as the NH₄⁺ translational diffusion is slow and proton exchange between NH₄⁺ ions and the acidic protons is negligible.     

Chalcogen based treatment of InAs with [(NH4)2S/(NH4)2SO4]

A sulphur based chemical, ([(NH₄)₂S/(NH₄)₂SO₄]) to which S has been added not previously reported for the treatment of (111)A InAs surfaces is introduced and benchmarked against the commonly used passivants Na₂S·9H₂O and ((NH₄)₂S + S), using Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It has been found that the native oxide layer present on the InAs surface is more effectively removed when treated with ([(NH₄)₂S/(NH₄)₂SO₄] + S) than with ((NH₄)₂S + S) or Na₂S·9H₂O. AES depth profiles of the sulphurized layers revealed the formation of a thin (less than 8.5 nm) In–S surface layer for both ((NH₄)₂SO₄ + S) and ([(NH₄)₂S/(NH₄)₂SO₄] + S) treatments. No evidence for the formation of As―S bonds was found. Treatment with ([(NH₄)₂S/(NH₄)₂SO₄] + S) also affected a significant improvement compared to the more established sulphur treatments in the surface morphology of the otherwise poor as-received n-InAs (111)A surface.     

Thermal,dielectric and conductivity studies on PVA/Ionic liquid [EMIM][EtSO4] based polymer electrolytes

Polymer electrolyte films of (PVA+15 wt% LiClO₄)+x wt% Ionic liquid (IL) 1-ethyl-3-methylimidazolium ethylsulfate [EMIM][EtSO₄] (x=0, 5, 10, 15) were prepared by solution cast technique. These films were characterized using TGA, DSC, XRD and ac impedance spectroscopic techniques. XRD result shows that amorphosity increases as the amount of the IL in PVA+salt (LiClO₄) is increased. DSC results confirm the same (except (PVA+15 wt% LiClO₄)+10 wt% IL). The dielectric and conductivity measurements were carried out on these films as a function of frequency and temperature. The addition of IL significantly improved the ionic conductivity of polymer electrolytes. Relaxation frequency vs. temperature plot for (PVA+15 wt% LiClO₄)+x wt% IL were found to follow an Arrhenius nature. The dielectric behavior was analyzed using real and imaginary parts of dielectric constant, dielectric loss tangent (tan δ) and electric modulus (M′ and M″).     

Paramagnetic properties of the spinel-type Al1−xMnx-sulphate salts for its pillared intercalation into a clay mineral

Paramagnetic interactions on Manganese ions substituted for Aluminium ions by x-mole fraction (x=0.01–0.1) for the spinel-type Al-complexes, [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺, were investigated. The superconducting quantum interference detection (SQUID) measurements showed a small susceptibility of the order of 10⁻⁶ emu/g originated from the Mn ion, and from the saturation value of the DC-magnetization for the 10 mol% Mn concentration, the spin S-value was determined as 2.8 close to its divalent state spin 5/2. The 9 GHz electron paramagnetic resonance (EPR) study revealed that the number of Mn²⁺ ions embedded in the axial crystal field had a characteristic maximum at the stoichiometric molar concentration Al/(Al+Al₁₂) equal to 7.69%, and the Infrared absorption (IR) experimental result verified this evidence. A theoretical approach was made separately for the concentrations below and above 7.69%. The higher-frequency 24 and 97 GHz EPR measurements examined effectively the result of the crystal field analysis in the 9 GHz, except for the small line splittings due to the higher-order Zeeman and hyperfine effects of the S-state ion. The intercalation of Al_1−xMn_x-sulphate (x=0.07) as a pillaring agent into a clay mineral, montmorillonite, was confirmed from the X-ray diffraction results.     

Incorporation of Ce3+ in crystalline Gd-silicate nanoclusters formed in silica

Structural and optical properties of sol–gel silica based glassceramics doped with 0.1 mol% Ce and codoped with Gd at high concentrations, from 5 mol% up to 40 mol%, are investigated and compared to those of analogous samples doped only with Ce. Raman scattering, transmission electron microscopy, and x-ray diffraction reveal the formation of Gd apatite-like silicate (Gd_4.67O(SiO₄)₃) and of Gd pyrosilicate (Gd₂Si₂O₇) nanophases whose morphology and crystallinity depend on the Gd concentration and thermal treatments. Optical absorption measurements demonstrate the role of the densification atmosphere in modifying the charge state of Ce ions. The incorporation of Ce³⁺ ions in the nanophases is put in evidence by photo- and radio-luminescence results.     

Quantification of local oxygen defects around Yttrium ions for yttria-doped ceria–zirconia ternary system

Local coordination structure around Yttrium ions in CeO₂–Y₂O₃ binary and [(CeO₂)_x(ZrO₂)_1?x]_0.8(YO_1.5)_0.2 (x = 0.0 ~ 1.0) ternary system has been investigated by ⁸⁹Y MAS-NMR. NMR spectra are found to be consisted of multiple peaks that can be assigned to 6-, 7- and 8-oxygen coordinated Yttrium ions. Compositional dependence of the spectrum was observed and compared with the previous results for ZrO₂–Y₂O₃ binary system. The present investigation suggested the degree of localization of the oxygen vacancy around the cation is in the order of Zr⁴⁺ > Y³⁺ > Ce⁴⁺. The degree of the oxygen vacancy preference for each cation was quantitatively determined for CeO₂–ZrO₂–Y₂O₃ ternary system the first time.     

Super-protonic phase transition and fast ionic conductivity of Li+ in [Li0.2(NH4)0.8]2TeCl6

The differential scanning calorimetry diagram of [Li_0.2(NH₄)_0.8]₂TeCl₆ showed one anomaly at 526 K accompanied with a shoulder at 505 K.The conductivity plot exhibits two anomalies at 496 and 526 K, which characterize the beginning and the end of the crossing to superionic conductor state. The low temperature conduction is ensured essentially by Li⁺. A sudden jump confirms the presence of a superionic protonic transition related to the fast motion of Li⁺ and H⁺ ions. Above 526 K, the high temperature phase is characterized by high electrical conductivity (10^− 3 Ω^− 1 m^− 1) and low activation energy (E_a < 0.3 eV).The dielectric constant evolution as a function of frequency and temperature revealed the same anomaly.Transport properties in this material appear to be due to Li⁺ and H⁺ ions' hopping mechanism.     

Structural and electrical properties of tellurovanadate glasses containing Li2O

Glassy materials are promising intercalation compounds, due to their open network structure and absence of grain boundaries. Some glasses containing alkali ions and a high concentration of transition metal ions can present mixed ionic-electronic conductivity and are therefore potential candidates for application as cathode material in Li-ion batteries. The present work is devoted to the ternary system xLi₂O–(1 − x)[0.3V₂O₅–0.7TeO₂] with 0 ≤ x ≤ 0.4. These compounds were prepared by heat treatment in air at 800 °C followed by traditional quenching. Raman spectroscopy and ⁵¹V nuclear magnetic resonance measurements were performed in order to highlight the structural short range order modifications induced by the introduction of the Li₂O network modifier. These structural effects can be related to the electrical behaviour, as studied by complex impedance spectroscopy measurements.     

Optical detection of organic hydrides with platinum-loaded tungsten trioxide

Tungsten trioxide powder with loading 0.1 wt% platinum (Pt/WO₃) was prepared for optical detection of organic hydrides such as cyclohexane, decalin by impregnation with PtCl₆^2? and subsequent calcination in air at 500 °C. The scanning electron microscopic observation of Pt/WO₃ shows that the Pt particles with mean diameters of 80–100 nm were on the surface of the WO₃ powder. The Pt/WO₃ showed coloration for 13% cyclohexane at higher 100 °C and for 1.3% cyclohexane at 200 °C. The in-situ XRD results of the Pt/WO₃ in coloring/bleaching change indicate that the coloring of Pt/WO₃ was caused by transformation of WO₃ to tungsten bronze. The analysis of reacted gas demonstrates that Pt on WO₃ produces only hydrogen and benzene through dehydrogenation of cyclohexane over 100 °C. It was founded that the Pt/WO₃ has potential of optical detection of organic hydrides by heating at higher 100 °C.     

The studies on structural and thermal properties of delithiated LixNi1/3Co1/3Mn1/3O2 (0 < x ≤ 1) as a cathode material in lithium ion batteries

The structural and thermal properties of the delithiated Li_xNi_1/3Co_1/3Mn_1/3O₂ (0 < x ≤ 1) material have been investigated by using diffraction and thermoanalytical techniques such as XRD and TG-DSC methods. XRD result shows that the delithiated materials maintain the O3-type structure with defined stoichiometric number at the range of 0.24 < x ≤ 1, exhibiting good crystal structural stability. The cobalt and nickel ions in the delithiated materials change their valence state (i.e. Co³⁺ to Co⁴⁺ and Ni³⁺ to Ni⁴⁺) when x < 0.49; the irreversible changes of the transformation may affect the first cycle of charge–discharge efficiency of the materials. A comparison of the results of TG-DSC with TPD-MS shows that the irreversible change of oxygen species during the delithiation process of Li_xNi_1/3Co_1/3Mn_1/3O₂ have great influence on the structural and thermal stability and reversibility of the materials.     

Increase of the blue upconversion emission in YAG:Tm3+ nanopowders by codoping with Yb3+ ions

The YAG nanopowders were prepared by a co-precipitation method using nitrate and ammonium hydrogen carbonate as raw materials. To obtain homogenous precipitate, reverse-strike (adding salt solutions to the precipitant solution) technique was adopted. Therefore, single (Tm³⁺) and codoped (Tm³⁺–Yb³⁺) YAG nanopowders with a size between 40–90 nm have been obtained.Blue upconversion emission at around 480 nm has been found in YAG: Tm³⁺ nanopowders under excitation to the ³H₄ level of Tm³⁺ at around 800 nm. However, this upconversion emission in nanopowders codoped with Tm³⁺–Yb³⁺ ions is increased by a factor of about 10. The analysis of the temporal evolution of the involved levels and the dependence of the upconversion intensity on the pump power at 800 nm allowed to distinguish the upconversion mechanism. In YAG: Tm³⁺ nanopowders the upconversion mechanism is due to excited state absorption processes. However, in the codoped samples, Yb³⁺ ions acts as the sensitizers; in consequence, the blue upconversion is strongly increased.     

Luminescence and defect studies of YAlO3:Dy3+, Sm3+ single crystals exposed to 100 MeV Si7+ ion beam

Ionoluminescence (IL) and photoluminescence (PL) spectra for different rare earth ions (Sm³⁺ and Dy³⁺) activated YAlO₃ single crystals have been induced with 100 MeV Si⁷⁺ ions with fluence of 7.81×10¹² ions cm^?2. Prominent IL and PL emission peaks in the range 550–725 nm in Sm³⁺ and 482–574 nm in Dy³⁺ were recorded. Variation of IL intensity in Dy³⁺ doped YAlO₃ single crystals was studied in the fluence range 7.81×10¹²–11.71×10¹² ions cm^?2. IL intensity is found to be high in lower ion fluences and it decreases with increase in ion fluence due to thermal quenching as a result of an increase in the sample temperature caused by ion beam irradiation. Thermoluminescence (TL) spectra were recorded for fluence of 5.2×10¹² ions cm^?2 on pure and doped crystals at a warming rate of 5 °C s^?1 at room temperature. Pure crystals show two glow peaks at 232 (Tg₁) and 328 °C (Tg₂). However, in Sm³⁺ doped crystals three glow peaks at 278 (Tg₁), 332 (Tg₂) and 384 °C (Tg₃) and two glow peaks at 278 (Tg₁) and 331 °C (Tg₂) in Dy³⁺ was recorded. The kinetic parameters (E, b s) were estimated using glow peak shape method. The decay of IL intensity was explained by excitation spike model.     

Proton spin relaxation of molecules adsorbed in NaY and NaPtY zeolite; The influence of adsorbed water on the distribution of atomic platinum

The longitudinal proton spin relaxation time T₁ of molecules adsorbed in commercial zeolites is predominantly caused by paramagnetic impurities, typically of the order of 0.1 wt% of iron. If only 1 wt% of platinum is introduced into the zeolite (as [Pt(NH₃)₄]²⁺), T₁ of water is enhanced up to one order of magnitude, as was shown in a preceding paper. The reason for this effect is that, under suitable thermal pretreatment of the Pt-exchanged zeolite, the Pt²⁺ ions are reduced by the ammonia to atomic platinum and part of the Pt atoms migrate preferentially to Fe³⁺ ions. Thus, Fe³⁺ ions, controlling T₁, are covered and up to 90% of paramagnetic sites for water is occupied by Pt atoms. In this paper, it is shown that Pt atoms preferentially migrate to Fe³⁺ ions only under the influence of water and that, therefore, various adsorbed organic molecules do not show the enhancement of T₁, unless the NaPtY zeolite is suitably pretreated with water before the organic molecules are adsorbed.     

X-ray excited luminescence and photoluminescence of Bi4(GeO4)3 glass-ceramics

Bi₄(GeO₄)₃ glass materials have been characterized by X-ray excited luminescence, photoluminescence and cathodo-luminescence measurements. The materials were obtained by crystallization at different temperatures and their spectroscopic parameters were compared before and after crystallization. Thermoluminescence curves recorded after electron irradiation of BGO glass behave similarly to BGO crystals, showing several peaks between 408 K (135 °C) and 610 K (337 °C). The differences between the Bi₄(GeO₄)₃ crystals and glass materials are believed to result from the random distribution of GeO₄ tetrahedra around Bi³⁺ ions which influences the photoluminescence and TL parameters. The CL images of glass-ceramic samples obtained by partial crystallization at 600 °C show luminescent crystalline structures, which are probably responsible for the increase in scintillation efficiency.     

Structural chemistry and zeolitic properties of mixed oxalates with two open-framework types based on eight coordinate metals

Two families of open-framework materials have been obtained from the assembly of MO₈ polyhedra and oxalate groups as building blocks. The compounds can be formulated as [MM′(C₂O₄)₄]²⁻(M″_y)²⁺ · (4 + x)H₂O (y is 2 for monovalent M″ metals and 1 for divalent M″ metals), in which the sum of the valences of the two metals M and M′ involved in the anionic framework is six. The water molecules and counter cations, located in the voids of the structure, lead to zeolitic or cation dynamic properties.     

Synthesis and electrochemical characterization of M2Mn3O8 (M = Ca,Cu) compounds and derivatives

M₂Mn₃O₈ (M = Ca²⁺, Cu²⁺) compounds were synthesized and characterized in lithium cells. The M²⁺ cations, which reside in the van der Waals gaps between adjacent sheets of Mn₃O₈⁴⁻, may be replaced chemically (by ion-exchange) or electrochemically with Li. More than 7 Li⁺/Cu₂Mn₃O₈ may be inserted electrochemically, with concomitant reduction of Cu²⁺ to Cu metal, but less Li can be inserted into Ca₂Mn₃O₈. In the case of Cu²⁺, this process is partially reversible when the cell is charged above 3.5 V vs. Li, but intercalation of Cu⁺ rather than Cu²⁺ and Li⁺/Cu⁺ exchange occurs during the subsequent discharge. If the cell potential is kept below 3.4 V, the Li in excess of 4 Li⁺/Cu₂Mn₃O₈ can be cycled reversibly. The unusual mobility of + 2 cations in a layered structure has important implications both for the design of cathodes for Li batteries and for new systems that could be based on M²⁺ intercalation compounds.     

Spectral structure of barium–phosphate–silicate phosphor Ba10(PO4)4(SiO4)2:EuM+

The new apatite–silicate phosphor doped with Eu ions in Ba₁₀(PO₄)₄(SiO₄)₂ matrix was synthesized through solid-state reaction. It was found that the as-synthesized phosphor displayed apparent mixture of band and line emission peaks giving rise to pseudo white light. The narrow emission bands peaking at 410 nm can be assigned to the 4f⁶5d→4f⁷(⁸S_7/2) transition of Eu²⁺ ions, and the other band at 507 nm is ascribed to anomalous fluorescent emission. One group of line emission peaking at 595 nm and 613 m were due to the ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transition of Eu³⁺ ions. The occurrence of photostimulated luminescence and discrete emission lines in violet (410 nm), green (507 nm) and red (595 nm and 613 nm) colors indicate that this material has potential application in fields of white-light-emitting.