Synthesis, characterization and device application of hot-pressed solid polymer electrolytes:(1 − x) PEO:x NaHCO3

Synthesis and io n transport characterization of hot-pressed solid polymer electrolyte (SPE) membranes:(1 ? x) poly (ethylene oxide) (PEO):x NaHCO₃, where 0 < x < 50 wt.%, have been reported. SPE films have been synthesized using a hot-press technique in place of the traditional solution-cast method. A conductivity enhancement of the two orders of magnitude was achieved in SPE film:70PEO:30NaHCO₃ and this composition has been referred to as optimum conducting composition (OCC). Materials characterization was done with the help of XRD, SEM, FTIR, DSC and TGA techniques. The ion transport behavior in SPE membranes has been discussed on the basis of experimental measurements on their ionic conductivity (σ), ionic mobility (μ) and some other important parameters. A solid-state polymer battery was fabricated using SPE OCC at room temperature, as a device application.     

A comparative raman study of the local structure in (Ge2S3) x (As2S3)1-x and (GeS2) x (As2S3)1−x glasses

The Raman spectra of glasses in the ternary (Ge₂S₃) _x (As₂S₃)_1−x and (GeS₂) _x (As₂S₃)_1−x systems are reported. It is shown that the degree of disorder in the (Ge₂S₃) _x (As₂S₃)_1−x glasses increases with an increase in the Ge content. The differences in the spectra of glasses with the same molar content of As₂S₃ are discussed in terms of the changes occurring in the local structure due to deviations from the stoichiometry. The observed changes in the intensity of the boson peak indicate changes in the medium-range order structure of the glasses under study.     

Peculiar dielectric properties of (1-x)(K,Na)(Nb,Sb)O3−x(Bi,Na)ZrO3 ceramics

In spite of the significance from both scientific and technological viewpoints, systematical studies on the dielectric spectra of (K,Na)NbO₃-based lead-free ceramics particularly in the poled state had been scarcely performed so far. In this study, the compositional series of (1-x)(K_0.48Na_0.52)(Nb_0.96Sb_0.04)O₃?x(Bi_0.50Na_0.50)ZrO₃ ceramics were chosen representatively to shed more light on the characters of dielectric properties. All the ceramics in the unpoled state show dielectric spectra of large dispersion with the relaxational characteristic frequency higher than the measured upper limit of 60 MHz at room temperature. Additional resonance peaks due to the electromechanical coupling of piezoelectric effect appear and are accompanied by a large step-like reduction of dielectric permittivity ε′ in the dielectric spectra after poling. An abnormal phenomenon that poling induces the increase of low-frequency ε′ occurs in those ceramics with x ≥ 0.04 at room temperature, and is confirmed to associate closely with the orthorhombic-tetragonal and rhombohedral-orthorhombic polymorphic phase transitions. Further study of domain structure indicates that the origin of this abnormal phenomenon should be ascribed to the enhancement of domain-wall mobility because of the large reduction of domain-wall density due to the poling.     

Varistor and electrical properties of MgO.(Fe2O3)1−x(Bi2O3)x ceramics

In this study, MgO.(Fe₂O₃)_1−x(Bi₂O₃)_x (x = 0.01, 0.02, 0.04, 0.08) samples were prepared by the conventional ceramic process. Microstructure studies revealed that the samples contain MgFe₂O₄ grains surrounded by insulating Bi₂O₃-rich phases. DC electrical resistivity of the samples was increased by Bi₂O₃ content up to 1.1 MΩ.cm for the sample with x = 0.08. Current density- electric field investigations suggested that the samples with x = 0.01, 0.02 and 0.04 exhibited varistor properties. The sample with x = 0.01 showed excellent varistor properties with a non-linear coefficient of 45 and a threshold electric field value of 160 V/cm. Variation of D.C electrical conductivity versus temperature indicated that the activation energy values for the conduction were increased by Bi₂O₃ content from 0.334(5) eV to 0.857(5) eV. A.C electrical conductivity spectra of the samples obey the universal power law and the charge transport mechanism is based on electron hopping via sudden translational motion between the ferric and ferrous ions.     

Surface Exchange of Oxygen in La1−x Sr x FeO3−δ (x = 0, 0.1)

The electronic charge carrier concentration in La_1?x Sr _x FeO_3?δ was shown to depend on the partial pressure of O₂ (pO ₂). Chemical diffusion coefficient and surface exchange coefficient, k _chem, were determined by conductivity relaxation in O₂/N₂ and CO/CO₂ mixtures. k _chem was proportional to pO ₂ ^1.06 in O₂/N₂, while in CO/CO₂ k _chem was controlled by a reaction mechanism involving both CO and CO₂.     

Electrical,structural and thermal properties of nanoceramic (Bi2O3)1−x−y(Ho2O3)x(Tm2O3)y ternary system

Ho₂O₃ and Tm₂O₃ doped Bi₂O₃ composite electrolyte type materials for solid oxide fuel cells (SOFCs) operating at intermediate-temperature were investigated. The bismuth-based ceramic powders were produced by using conventional solid-state synthesis techniques. The products were characterized by means of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), differential thermal analysis/thermal gravimetry (DTA/TG), and the four-point probe technique (4PPT). XRD and DTA/TG measurements indicate that all of the samples have the stable fluorite type face centered cubic (fcc) δ-phase. 4PPT measurements were performed in the temperature range 150–1000 °C in air and these measurements showed that the electrical conductivity of the samples decrease with increasing amount of Tm₂O₃. This increase in the electrical conductivity of the samples could be attributed to the increase in the numbers of highly polarizable cations and oxide ion vacancies. The highest conductivity value was found as 5.31×10^?1 Ω cm^?1 for the (Bi₂O₃)_1?x?y(Ho₂O₃)_x(Tm₂O₃)_y ternary system (for x=20 and y=5 mol%) at 1000 °C. The activation energies of the samples were calculated from log σ graphics versus 1000/T. These calculated results showed that the translation motion of the charge carriers, oxygen vacancies, and space charge polarizations are responsible for the change in activation energy as a function of temperature.     

γ-irradiation hardness investigations of (PANI)1−x(Bi2Te3)x composites for thermistor applications

The (PANI)_1−x(Bi₂Te₃)_x composites were successfully synthesized. These composites have a simple physical combination of intrinsic conducting polymer and nanocrystal topological insulator materials which are promising new materials for unusual applications. The influence of γ-irradiation (100 kGy doses) on the performance of the (PANI)_1−x(Bi₂Te₃)_x composites was described by atypical techniques to assess the radiation hardness of the samples. X-ray diffraction and Raman spectroscopy measurements show the semi-crystalline phases, the other structural parameters, and the phonon modes. The compositional analysis and the morphological properties were investigated by energy-dispersive X-ray, while transmission electron microscopy imaging confirmed the morphology of the dopants of Bi₂Te₃ nanoparticles into the polyaniline (PANI) matrix, which shows the accumulation of the particles. Thermogravimetric analysis figured out the degradation behavior of the compositions. The representative electron spin resonance (ESR) signal exhibits a narrow single-line ESR spectrum for PANI/Bi₂Te₃ nanoparticle concentrations. (PANI)_1−x(Bi₂Te₃)_x illustrates unexpected ferromagnetic behavior that confirms the magnetic performance of the samples without introducing any magnetic dopants. The obtained materials showed promising performance for using such hybrid materials as a positive temperature coefficient thermistor.     

Dielectric and piezoelectric properties of (1−x)(Bi,Na)TiO3–x(Bi,K)TiO3 lead-free ceramics for piezoelectric energy harvesters

The piezoelectric and dielectric properties of the (1−x)(Bi,Na)TiO₃–x(Bi,K)TiO₃ (x=0.12, 0.14, 0.18, 0.20 and 0.30) lead-free ceramics were investigated. Specimens were prepared by the conventional mixed oxide method and sintered at 1170 °C in air. Scanning electron microscopy indicated that increasing x from 0.12 to 0.30 causes a decrease in the grain size. The (1−x)(Bi,Na)TiO₃–x(Bi,K)TiO₃ ceramics shows a homogeneous microstructure and excellent dielectric and piezoelectric properties. Specimens with optimum composition showed a piezoelectric charge constant d₃₃ of 166 pC/N, an electromechanical coupling factor k_p of 0.5, a dielectric constant ε_r of 1591.32 at 1 kHz and generated power output of 37.49 nW/cm².     

Density and surface tension of Se(90−0.9x )S(10−0.1x)Me x and Se(60−0.6x)S(40−0.4x)Me x (Me = Sb), Ge glass-forming meltsMe x (Me = Sb), Ge glass-forming melts

The properties of melts in the Se_(90−0.9x)S_(10−0.1x)Me _x and Se_(60−0.6x)S_(40−0.4x)Me _x (Me = Sb, Ge) systems (wherex ranges from 2.5 to 15 mol % with a step of 2.5 mol %) have been investigated. The density and surface tension of melts and the wetting angles of the PbSe semiconductor by melts are measured. The work of adhesion and adhesion strength of the glass coating are calculated. The experimental data are processed using the least-squares method, and the corresponding regression equations are derived. From the materials of the paper reported at the International Conference “Glasses and Solid Electrolytes” (St. Petersburg, 1999, May 17–19).     

Magnetic properties of ferrites-cobaltites Bi1 − x La x Fe1 − x Co x O3 (1.0 ≥ x ≥ 0.7) with a perovskite structure

The molar magnetic susceptibility (χ_mol) of Bi_{1 ? x} La _x Fe_{1 ? x} Co _x O₃ solid solutions (x = 1.0, 0.9, 0.8, or 0.7) with a crystal structure of rhombohedrally distorted perovskite (R $\bar 3$ c) has been investigated in the temperature range of 5–300 K in a 0.86 T magnetic field. In the temperature range where χ_mol depends on temperature T according to the Curie-Weiss law, the resulting effective magnetic moments of Fe³⁺ and Co³⁺ ions ( $\mu _{eff,Fe^{3 + } ,Co^{3 + } ,} \mu _{eff,Fe^{3 + } } $ and $\mu _{eff,Co^{3 + } } $ ) have been determined for the solid solutions under study. Fe³⁺ ions in the solid solutions have been found to be in the mixed intermediate spin (IS) and high spin (HS) states ( $\mu _{eff,Fe^{3 + } } $ is 4.26μ_B and 4.68μ_B for the temperature range of 5–100 and 150–300 K, respectively). It is shown that 8% Co³⁺ ions in LaCoO₃ at 5–19 K are in the paramagnetic IS state and they determine to a great extent the magnetic susceptibility. It is established that only 9% and 18% Co³⁺ ions in Bi_{1 ? x} La _x Fe_{1 ? x} Co _x O₃ solid solutions (x = 0.9 or 0.8) are in the paramagnetic IS state in the temperature ranges of 5–30 and 5–110 K, respectively, while the other ions are diamagnetic.     

Bond characteristics,sintering behavior and microwave dielectric properties of Ce2[Zr1−x(Ca1/3Sb2/3)x]3(MoO4)9 ceramics

Ce₂[Zr_1?x(Ca_1/3Sb_2/3)_x]₃(MoO₄)₉ (CZ_1?x(CS)_xM) (x = 0.02–0.10) ceramics were prepared by the conventional solid-state reaction method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips–Van Vechten–Levine (P–V–L) theory. Phase composition and microstructures were evaluated by scanning electron microscopy and X-ray diffraction patterns. Lattice parameters were obtained by Rietveld refinements based on XRD data. Excellent properties for Ce₂[Zr_0.96(Ca_1/3Sb_2/3)_0.04]₃(MoO₄)₉ ceramic sintered at 775 °C: ε_r = 10.68, Q×f = 85,336 GHz and τ_f = ?7.58 ppm/°C were achieved.     

Enhanced magnetic,ferroelectric, and photocatalytic properties of (1-x)BiFeO3-xBaTiO3 (0.0 ≤ x ≤ 0.4) powders

The magnetic, ferroelectric, and photocatalytic properties of (1-x)BiFeO₃-xBaTiO₃ (0.0 ≤ x ≤ 0.4) powders synthesized by sol-gel method have been investigated. X-ray diffractometry confirms that the phase of the samples changed from rhombohedral to cubic with the increase in BaTiO₃ content. The grain size decreases and the particle shape becomes homogeneous with the introduction of BaTiO₃. BaTiO₃ substitution enhances the multiferroic properties of the ceramics and the maximum remnant magnetization (0.261 emu/g) and remnant polarization (20 μC/cm²) have acquired in 0.8BiFeO₃-0.2BaTiO₃ and 0.7BiFeO₃-0.3BaTiO₃, respectively. The absorbance in ultraviolet and visible light regions is improved obviously for powder with x = 0.3. The energy band gap of the samples decreases from 2.06 eV to 1.57 eV with the introduction of BaTiO₃, indicating that the excitation rate of photogenerated electron-hole pairs is improved. The highest methylene blue degradation efficiency of ~62% within 3 h under the visible light is achieved in the 0.7BiFeO₃-0.3BaTiO₃ which can be attributed to its suitable energy band gap and large remnant polarization.     

Synthesis,structural, electrical and magnetic properties of Bi2Fe4-xGaxO9 (0 ≤ x ≤ 1.6)

We investigate the electrical and magnetic properties of the Bi₂Fe_4-xGa_xO₉ (0?≤?x?≤?1.6) polycrystalline samples synthesized via solid-state reaction technique. Magnetic susceptibility measurements reveal that lightly doped samples (x?<?0.8) undergo successive transitions, from high-temperature paramagnetic to antiferromagnetic phase followed by a low-temperature spin-glass state while the samples with heavy doping (x?>?0.8) demonstrate paramagnetic to spin-glass (SG) transition. The variation of irreversible temperature obtained from zero field cooling (ZFC) and field cooling (FC) susceptibilities versus measured magnetic field and low-temperature magnetic hysteresis (M-H) loops support the existence of spin-glass phase. The dielectric constant (?_r) of Bi₂Fe_4-xGa_xO₉ with Ga-dilution reveals a weak-temperature sensitivity in high-temperature range (300?K?≤?T?≤?550?K), which is advantageous for high temperature capacitor applications and electronic devices.     

Synthesis,Microstructure, and Mechanical Properties of Ti3Sn(1−x)AlxC2 MAX Phase Solid Solutions

Ti₃Sn_(1−x)Al_xC₂ MAX phase solid solutions are successfully synthesized from different reactant mixtures. Rietveld refinement allows to carefully characterize their structures and the ocathedra and trigonal prims distortion parameters as a function of the Al content. Mechanical properties of solid solutions are studied from nanoindentation experiments and dynamic resonant method. It is shown that solid solution hardening is not operative in this system. Elastic modulus is found to increase from Ti₃SnC₂ to Ti₃AlC₂, and such a result is discussed in terms of Ti–A bond stiffness.     

Correlation between local structure variations and critical temperature of (Bi1.6Pb0.4Sr2Ca2Cu3O10+δ)1-x(TiO2)x superconductor

TiO₂ doping content affects the critical temperature (T_c) and the variations of local structure on Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ. The (Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ)_1-x(TiO₂)_x samples were fabricated with the solid-state reaction process, where x = 0, 0.002, 0.004, 0.006, 0.008, and 0.01. The T_c values of the samples were obtained by measuring resistivity versus temperature, indicating that T_c gradually decreased with increasing doping content (x). To explain the obtained degradation of T_c, carrier properties, role of interlayer coupling, and local structure were systematically investigated using Azlamozov–Larkin theory and its Lawrence–Doniach modification for strong anisotropic superconductors. The calculation of excess conductivity at the mean field region showed that the c-axis coherence length (ξ_c) and the effective inter-layering spacing (d) increased with increasing doping content. X-ray diffraction patterns also showed that the bond distances increased with increasing TiO₂ content. The copper valence (V) and carrier concentration (p) of the samples were determined by analyzing the Cu L_2,3-edge X-ray absorption near edge structure spectra. The values of V and p showed the same trend of decreasing with increasing x. A close correlation between the changes in local structure parameters and degradation of T_c of (Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ)_1-x(TiO₂)_x was then probably concluded.     

Temperature-independent permittivity of xBaTiO3–(1−x)(0.5Bi(Mg1/2Ti1/2)O3–0.5BiScO3) ceramics

xBaTiO₃–(1−x)(0.5Bi(Mg_1/2Ti_1/2)O₃-0.5BiScO₃) or xBT–(1−x)(0.5BMT–0.5BS) (x=0.45–0.60) ceramics were prepared by using the conventional mixed oxide method. Perovskite structure with pseudo-cubic symmetry was observed in all the compositions. Dielectric measurement results indicated that all the samples showed dielectric relaxation behavior. As the content BaTiO₃ was decreased from 0.60 to 0.45, temperature coefficient of permittivity (TCε) in the range of 200–400 °C was improved from −706 to −152 ppm/°C, while the permittivity at 400 °C was increased from 1208 to 1613. The temperature stability of permittivity was further improved by using 2 mol% Ba-deficiency. It was found that lattice parameter and grain size of the 2 mol% Ba-deficient ceramics were smaller than those of their corresponding stoichiometric (S) counterparts, with TCε in the range of 200–400 °C to be improved noticeably. For example, TCε of the Ba-deficiency sample with x=0.45 was −75 ppm/°C in the temperature range of 200–400 °C and the permittivity was 1567 at 400 °C. The results obtained in this work indicated that xBT–(1−x)(0.5BMT–0.5BS) ceramics are very promising candidates for high temperature capacitor applications.     

Synthesis and lithium ionic conductivity of Li3−2x(In1−xZrx)2(PO4)3 (0≦x≦0·20)

Lithium ion conductors, Li_3−2x(In_1−xZr_x)₂(PO₄)₃ (0≦x≦0·20), were synthesized by a solid state reaction. A superionic conductive phase of Li₃In₂(PO₄)₃ was stabilized down to room temperature, assisted by the substitution of Zr⁴⁺ for In³⁺ sites of Li₃In₂(PO₄)₃. TG-DTA analysis indicated no phase transition in the samples with x superior to 0·05. The substituted samples showed much higher ionic conductivity by a couple of magnitude than that of Li₃In₂(PO₄)₃. In particular, the highest conductivity at room temperature was 1·42×10⁻⁵ Scm⁻¹ for Li_2·8(In_0·9Zr_0·1)₂(PO₄)₃. Thin films with the composition of Li_2·8(In_0·9Zr_0·1)₂(PO₄)₃ was prepared by a sol–gel method. A coating solution was made from lithium isopropoxide, indium isopropoxide, zirconium isopropoxide and diphosphorus pentaoxide. Well crystallized films were obtained on silicon dioxide and quartz glass substrates by dropping the coating solution, followed by firing over 873 K. In the temperatures above 473 K the lithium ionic conductivity of the film was slightly higher than that of sintered samples prepared by the solid state reaction at 1373 K.     

Structural and ion transport properties of [(AgI)x(AgBr)0.4−x](LiPO3)0.6 and (AgBr)x(LiPO3)(1−x) solid electrolytes

The (AgBr)_x(LiPO₃)_(1−x) (x=0.4 and 0.5) and [(AgI)_x(AgBr)_0.4−x](LiPO₃)_0.6 (x=0.1, 0.2, and 0.3) superionic electrolytes have been prepared by conventional melt quenching using a twin roller. These electrolytes are characterized by X-ray diffraction, SEM, and energy dispersive X-ray analysis (EDAX) for structural investigation. Electrical characterizations have been carried out by the AC impedance analysis. The conductivity of LiPO₃ glassy system at room temperature is improved by doping with the silver bromide (AgBr)_x(LiPO₃)_(1−x) and the mixture of silver iodide, silver bromide (AgI-AgBr-LiPO₃ system) up to 10⁻⁵ and 10⁻³ Ω⁻¹ cm⁻¹, respectively (improvements by four or five orders of magnitude). The frequency response of ionic conductivity has been analyzed by universal dynamic response model (Jonscher's law) and AC conductivity data are fitted using the Jonscher's power law. The conductivity values obtained by the power law and impedance plots are comparable. The frequency exponent (n) has a value between 0 and 1. The AgI-AgBr-LiPO₃ system shows the mixed alkali effect. Summerfield scaling master curve is temperature dependent, which may be due to the contribution of the both lithium and silver ions to ionic conduction.     

Synthesis and characterization of quarternary Ti3Si(1−x)AlxC2 MAX phase materials

Ti₃Si_(1−x)Al_xC₂ (x=0–1) quarternary MAX phase materials were prepared by spark plasma sintering of TiC, Ti, Si and Al powder mixtures at 1200 °C. Effect of Al addition on lattice parameters, density and hardness were investigated. Impurities are limited to binary phases of TiC and Ti₅Si₃. No multinary compound other than Ti₃Si_(1−x)Al_xC₂ can be detected. TiC exists as impurity in all samples and trace amount of Ti₅Si₃ can be detected in Samples x=0.1–0.6. Oxidation of Al cannot be avoided although all sintering were performed under vacuum and trace amount of Al₂O₃ can be found in all samples with Al addition. Experimental results show that the lattice parameters a and c increase linearly with increasing Al content for x=0–1. The lattice variations are strongly anisotropic and follow Vegard׳s law. Both density and hardness decrease as Al content increases. The linear variation of lattice parameters, d spacings of crystalline faces and density against Al concentration suggest that continuous solid solutions of Ti₃Si_(1−x)Al_xC₂ (x=0–1) may have been formed between Ti₃SiC₂ and Ti₃AlC₂.