Studies of structure, thermal, and electrical properties for Cs 5 H 3 (SO 4 ) 4 crystal

Electrical conductivity, differential scanning calorimetry, and X-ray diffraction measurements were performed on a pentacesium trihydrogen tetrasulfate, Cs₅H₃(SO₄)₄, crystal. The transition entropy at a superionic phase transition and the activation energy of proton migrations in the superionic phase were determined to be 58.2 J K⁻¹ mol⁻¹ and 0.48 eV, respectively. The crystal structure of Cs₅H₃(SO₄)₄ at room temperature was refined. The electrical conduction in Cs₅H₃(SO₄)₄ was discussed with the refined structure.     

Transport properties of hexanoyl chitosan-based gel electrolyte

Films of hexanoyl chitosan-based polymer electrolyte were prepared by the technique of solution casting. The effect of plasticizer on the transport properties of hexanoyl chitosan:lithium trifluoromethanesulfonate (LiCF₃SO₃) electrolytes have been investigated. The plasticizer used was ethylene carbonate (EC). The highest room temperature conductivity achieved in the EC-plasticized hexanoyl chitosan-based electrolytes is 2.75×10⁻⁵ S cm⁻¹. The Rice and Roth model was used to explain the variations in the dc conductivity observed. The exponent, s, in Jonscher’s universal power law equation σ(ω)=σ _dc+Aω ^s , was analyzed as a function of temperature for the sample containing 30 wt% of EC. The analysis suggests that the conduction mechanism follows that proposed by the overlapping large polaron tunneling model.     

Impedance spectroscopy studies of poly (methyl methacrylate)-lithium salts polymer electrolyte systems

In the present work, five systems of samples have been prepared by the solution casting technique. These are the plasticized poly(methyl methacrylate) (PMMA-EC) system, the LiCF₃SO₃ salted-poly(methyl methacrylate) (PMMA-LiCF₃SO₃) system, the LiBF₄ salted-poly(methyl methacrylate) (PMMA-LiBF₄) system, the LiCF₃SO₃ salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiCF₃SO₃) system, and the LiBF₄ salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiBF₄) system. The conductivities of the films from each system are characterized by impedance spectroscopy. The room temperature conductivity in the pure PMMA sample and (PMMA-EC) system is 8.57 × 10⁻¹³ and 2.71 × 10⁻¹¹ S cm⁻¹, respectively. The room conductivity for the highest conducting sample in the (PMMA-LiCF₃SO₃), (PMMA-LiBF₄), ([PMMA-EC]-LiCF₃SO₃), and ([PMMA-EC]-LiBF₄) systems is 3.97 × 10⁻⁶, 3.66 × 10⁻⁷, 3.40 × 10⁻⁵, and 4.07 × 10⁻⁷ S cm⁻¹, respectively. The increase in conductivity is due to the increase in number of mobile ions, and decrease in conductivity is attributed to ion association. The increase and decrease in the number of ions can be implied from the dielectric constant, ɛ_r-frequency plots. The conductivity–temperature studies are carried out in the temperature range between 303 and 373 K. The results show that the conductivity is increased when the temperature is increased and obeys Arrhenius rule. The plots of loss tangent against temperature at a fixed frequency have showed a peak at 333 K for the ([PMMA-EC]-LiBF₄) system and a peak at 363 K for the ([PMM-EC]-LiCF₃SO₃) system. This peak could be attributed to β-relaxation, as the measurements were not carried out up to glass transition temperature, T _g. It may be inferred that the plasticizer EC has dissociated more LiCF₃SO₃ than LiBF₄ and shifted the loss tangent peak to a higher temperature. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006     

Ion transport in proton conducting solid polymer electrolytes

In this communication the ion transport properties of polyvinyl alcohol complexed with orthophosphoric acid (H₃PO₄) have been investigated. The proton conduction is confirmed by hydrogen gas evolved at the cathode of the coulometer and the transference number of H⁺ ion has been determined. The transient ionic current (TIC) technique has been used to detect the mobile ionic species and their mobilities are evaluated. The ionic mobility was found to be of the order of 10⁻⁴ cm².V⁻¹.s⁻¹ for H⁺ ions. It is observed that the bulk electrical conductivity increases with the temperature following the Arrhenius type behaviour. Variation of charge carrier concentration with the molar ratio of H₃PO₄ in the sample reveals that the carrier concentration is largely affected by the amount of dopant in the complexes.     

Conductivity studies of starch-based polymer electrolytes

A proton-conducting polymer electrolyte based on starch and ammonium nitrate (NH₄NO₃) has been prepared through solution casting method. Ionic conductivity for the system was conducted over a wide range of frequency between 50 Hz and 1 MHz and at temperatures between 303 K and 373 K. Impedance analysis shows that sample with 25 wt.% NH₄NO₃ has a smaller bulk resistance (R _b) compared to that of the pure sample. The amount of NH₄NO₃ was found to influence the proton conduction; the highest obtainable room temperature conductivity was 2.83 × 10⁻⁵ S cm⁻¹, while at 100 °C, the conductivity in found to be 2.09 × 10⁻⁴ S cm⁻¹. The dielectric analysis demonstrates a non-Debye behavior. Transport parameters of the samples were calculated using the Rice and Roth model and thus shows that the increase in conductivity is due to the increase in the number of mobile ions.     

Infrared spectra of BeSO4.4H2O and its deuterated analogue at 110K in 1200–250 cm−1 region

IR absorption spectra of BeSO₄.4H₂O and its deuterated analogue are reported in the region 1200–250 cm⁻¹ at 110 K. The half-widths and relative integrated intensities of the bands are also reported. The study largely confirms the assignments for thev ₃ andv ₄ modes of SO ₄ ²⁻ ion and thev ₃ mode of Be(aq) ₄ ²⁺ , complex as made by Diemet al. The assignments of the other modes of SO ₄ ²⁻ and Be(aq) ₄ ²⁺ , and the librational modes of water are given a more solid footing as result of the present investigation.     

Structural and electrical characterisation of strontium zirconate proton conductor co-sputter deposited coatings

SrZr_1−x Y _x O₃ coatings were co-sputtered from metallic Zr–Y (84–16 at.%) and Sr targets in the presence of a reactive argon–oxygen gas mixture. The structural and chemical features of the film have been assessed by X-ray diffraction and scanning electron microscopy. The electrical properties have been investigated for different substrates by Complex Impedance Spectroscopy as a function of crystalline state, temperature and atmosphere. The as-deposited coatings are amorphous and crystallise after annealing at 673 K for 2 h under air. The stabilisation of the perovskite structure is a function of the nominal composition. The films are dense and present a good adhesion on different substrates. Crystallisation and mechanical stresses are detected by alternating current (AC) impedance spectroscopy. Significant ionic conductivity in the 473–823 K temperature range is evidenced in air. Two different conduction regimes in the presence of steam are attributed to a modification of the charge carrier nature. In spite of low conductivity values (σ ~10⁻⁶ S.cm⁻¹ at 881 K), the activation energies are in agreement with that of Y-doped strontium zirconate ceramics (~0.7 eV in air).     

Infrared spectra of BeSO4.4H2O and its deuterated analogue in 4000–1200 cm−1 region

IR spectra of BeSO₄.4H₂O and its deuterated analogue at ∼300 K and ∼110 K are reported in the region 4000–1200 cm⁻¹ using thin film and nujol mull techniques. The observed bands have been assigned as the internal modes of the water and the overtones and combinations of various modes using the recently revised assignments of SO₄ ²⁻ and Be(aq)₄ fundamentals in the region 1200–250 cm⁻¹ (Srivastavaet al 1976). The splitting of the internal modes of water has been discussed in the light of the effects of deuteration and cooling and it is shown that all the water molecules in a unit cell are asymmetric but crystallographically equivalent.     

The infrared and laser Raman spectra of K2Zn(SO4)2 · 6H2O

The Raman spectra of the single crystal of K₂Zn(SO₄)₂·6H₂O belonging toC _2h ⁵ space group in the 40–1200 cm⁻¹ region in different scattering geometries and their spectra ofthe microcrystalline salt in the 1500-50 cm⁻¹ region have been reported. The dynamics of the crystal has been described in terms of 186 phonon modes under the unit cell approximation. The weak bands in the region 400–900 cm⁻¹ have been assigned to the libratory modes of H₂O molecules in contradiction to the assignments reported by Ananthanarayanan. The ambiguities existing in the literature about the assignments ofν ₂ ^c andν ₅ ^c modes of [Zn(H₂O)₆]²⁺ have also been removed. The translatory and libratory modes of different units of the crystal have been identified and assignments are made using farir and Raman data on various isomorphous tutton salts. It has been inferred that both SO ₄ ²⁻ tetrahedron and [Zn(H₂O)₆]²⁺ octahedron undergo linear as well as angular distortions from their free state symmetries in the crystal.     

Nuclear Spin–Lattice Relaxation of Single Crystal Sr14Cu24O41

Nuclear spin–lattice relaxation rate T ₁ ⁻¹ has been measured for the ladder sites of two single crystals Sr₁₄Cu₂₄O₄₁ (Sr14-A,B) by ⁶³Cu NMR/NQR. The hole localization around 100 K appears as a peak in the T variation of T ₁ ⁻¹(NQR). On the other hand, it is suppressed in the T ₁ ⁻¹ (NMR) data under the magnetic field H ∼ 11 T, and a new peak appears around 20 K. T ₁ ⁻¹(NMR) around the peak is more enlarged for Sr14-B than for Sr14-A. Hence, holes on the ladders of Sr14-B tend to be more localized. This is considered to be an origin for the occurrence of the magnetic order in Sr14-B under H ∼ 11 T.     

Conductivity studies and ion transport mechanism in LiI–Li3PO4 solid electrolyte

Mixtures of LiI–Li₃PO₄ were sintered at low temperature. It was observed that the conductivity improved up to 10⁻³ S cm⁻¹ with the addition of LiI. Infrared technique (Fourier transform infrared spectroscopy [FTIR]) was employed to detect the presence of polyhedral structures. From the FTIR spectra of the binary samples with various weight percents of LiI, the PO₄ ³⁻ bands and the PO bending experienced small shifting which indicates that interaction has occurred. Alternating current conductivity versus frequency shows a linear variation suggesting that the behavior follows Jonsher power law. The conduction mechanism of LiI–Li₃PO₄ solid electrolyte follows the quantum mechanical tunneling model.     

Nuclear Spin Relaxation in Some Non-viscous Media Using the 181Hf Probe

Perturbed angular correlation (PAC) studies have been performed in liquid mercury, HCl media of different acid strengths, H₂O and H₃PO₄ using a ¹⁸¹Hf probe. It is found that, in case of H₂O, interaction between the nucleus and its excited atom following the β⁻ decay of ¹⁸¹Hf is a possible mechanism for the nuclear spin relaxation in this environment. In the liquid mercury and different acid media, however, the perturbations are found to arise due to molecular fluctuations.     

Determination of Trace Mercury by Solid Substrate-Room Temperature Phosphorimetry Quenching Method Based on Catalytic Effect of Hg2+on Formation of the Ion Association Complex [Sn(XO)6]4+·[(Fin)4]

A new method for the determination of trace mercury by solid substrate-room temperature phosphorimetry (SS-RTP) quenching method has been established. In glycine-HCl buffer solution, xylenol orange (XO) can react with Sn⁴⁺ to form the complex [Sn(XO)₆]⁴⁺. [Sn(XO)₆]⁴⁺ can interact with Fin⁻ (fluorescein anion) to form the ion associate [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which can emit strong and stable room temperature phosphorescence (RTP) on polyamide membrane (PAM). Hg²⁺ can catalyze H₂O₂ oxidizing the ion association complex [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which causes the RTP to quench. The ΔIp value is directly proportional to the concentration of Hg²⁺ in the range of 0.016–1.6 fg spot⁻¹ (corresponding concentration: 0.040–4.0 pg ml⁻¹, 0.40 μl spot⁻¹), and the regression equation of working cure is ΔIp=10.03+83.15 m Hg²⁺ (fg spot⁻¹), (r=0.9987, n=6) and the detection limit (LD) is 3.6 ag spot⁻¹(corresponding concentration: 9.0×10^–15 g ml⁻¹, the sample volume: 0.4 μl). This simple, rapid, accurate method is of high selectivity and good repeatability, and it has been successfully applied to the determination of trace mercury in real samples. The reaction mechanism for catalyzing H₂O₂ oxidizing the ion association complex ([Sn(XO)₆]⁴⁺·[(Fin)₄]⁻) SS-RTP quenching method to determine trace mercury is also discussed.     

Physicochemical properties of LiAl x Mn2 − x O4 and LiAl0.05Mn1.95O4 − y F y cathode material by the citric acid-assisted sol–gel method

LiAl _x Mn_2 − x O₄ and LiAl_0.05Mn_1.95O_4 − y F _y spinel have been successfully synthesized by citric acid-assisted sol–gel method. The structure and physicochemical properties of this as-prepared powder were investigated by electronic conductivity test, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge test in detail. The electronic conductivity decreases with increasing of the content of doped Al. XRD patterns show that the diffraction of LiAl_0.05Mn_1.95O_4 − y F _y samples is similar, with all the peaks indexable in the Fd3m space group, and a little impurity appears in the LiAl_0.05Mn_1.95O_3.8F_0.2 sample. SEM reveals that all LiAl_0.05Mn_1.95O_4 − y F _y powders have the uniform, nearly cubic structure morphology with narrow size distribution which is less than 500 nm. Galvanostatic charge–discharge test indicates that LiAl_0.05Mn_1.95O₄ has the highest discharge capacity and electrochemical performance among all LiAl _x Mn_2 − x O₄ samples after 50 cycles, and the initial discharge capacity of LiAl_0.05Mn_1.95O_4 − y F _y (y = 0, 0.02, 0.05, 0.1) is 123.9, 124.6, 124.9, and 125.0 mAh g⁻¹, respectively, and their capacity retention ratios are 94.2%, 94.9%, 91.7%, and 89.9% after 50 cycles, respectively. EIS indicates that LiAl_0.05Mn_1.95O_3.98F_0.02 have smaller charge transfer resistance than that of LiAl_0.05Mn_1.95O₄ corresponding to the extraction of Li⁺ ions.     

Crystallographic and magnetic phase transition in TlMnCl3

The results of our NMR, EPR and magnetic susceptibility measurements in the paramagnetic state of TlMnCl₃ are reported here. The NMR paramagnetic shift of thallium is found to be small but positive. Mn²⁺ EPR line is exchange narrowed. The susceptibility measurements indicate an antiferromagnetic transition. The heat of crystallographic phase transition ΔH, in TlMnCl₃ has been measured using differential scanning calorimetry. The crystallographic phase transition appears to be first order and ΔH is unusually low viz. 10 cal mole⁻¹. In the case of KMnF₃ Δ_H, which is reported here for the first time, is determined to be 2 cal mole⁻¹.     

Characterization of organic–inorganic hybrid layered perovskite and intercalated compound (n-C12H25NH3)2ZnCl4

We report on some electrical properties and solid–solid phase transitions of organic–inorganic hybrid layered halide perovskite and intercalated compound (n-C₁₂H₂₅NH₃)₂ZnCl₄ which is one member of the long-chain compounds of the series (n-C_nH_2n+1NH₃)_2,(n = 8–18). The complex dielectric permittivity ?*(ω,T) and the ac conductivity σ (ω,T) were measured as functions of temperature 100 K < T < 390 K and frequency 5 kHz < f < 100 kHz. Moreover, the differential scanning calorimetery and the differential thermal analysis thermograms were performed. The analysis of our data confirms the existence of a structural phase transition at T ≈ (362?±?2) K, where the compound changes its state from intercalation to non-intercalation with a drastic increase in the c-axis by about 16.4%.

The behavior of the frequency-dependent conductivity follows the Jonscher universal power law: σ (ω, T) α?^s(?,T). The mechanism of electrical conduction in the low-temperature phase (phase II) can be described as quantum mechanical tunneling model.     

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.     

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     

Infrared and raman studies on neodymium pentaphosphate and metaphosphates

The infrared and Raman spectra of crystalline samples of NdP₅O₁₄, NaNdP₄O₁₂ and KNdP₄O₁₂ are recorded. The spectra are analysed on the basis of vibrations of P=O, P-O, PO₂ and P-O-P groups. The P₄O ₁₂ ⁴⁻ ion has cyclic structures both in NaNdP₄O₁₂ and KNdP₄O₁₂ crystals. It has been inferred that the P-O-P bridges are stronger in metaphosphates.     

A stable NH4PO3-glass proton conductor for intermediate temperature fuel cells

A stable and conductive composite material based on NH₄PO₃ and amorphous oxides (SiO₂-P₂O₅) has been prepared by a wet-chemical route following with firing in ammonia. The composite showed high proton conductivity in both ambient air and humidified 5% H₂/Ar. A total conductivity of 6.0-19 mS/cm in the temperature range of 150-250 °C has been achieved. The conductivity (about 19 mS/cm) is stable in humidified 5% H₂/Ar during ageing at 175 °C for over 100 h. This material is a potential electrolyte for intermediate temperature fuel cells and other electrochemical devices.