Infralow-frequency dielectric response of Pb<Subscript>3</Subscript>O<Subscript>4</Subscript> polycrystalline layers

This paper reports on the results of the investigation into the frequency dispersion of the capacitance and dielectric loss in capacitor structures based on red lead Pb₃O₄. It is established that, in the range of frequencies f = 1.50 × 10^?3?0.25 Hz, the capacitance decreases and the dielectric loss tangent increases with increasing frequency. The frequency dependence of the electrical conductivity in an alternating-current electric field indicates the applicability of the hopping model of charge transfer under normal conditions. The role of a lone electron pair of Pb²⁺ cations in dielectric polarization is discussed.     

Synthesis and studies of trisubstituted biphthalonitrile/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic hybrid microspheres

New trisubstituted biphthalonitrile/magnetite (TSB/Fe₃O₄) magnetic hybrid microspheres were synthesized from TSB and FeCl₃ · 6H₂O using the method of one-stage thermal temperature crystallization of solvents. The morphology and structure of magnetic hybrid microspheres were inspected using a scanning electron microscope, IR Fourier spectroscopy, and X-ray diffraction. It was found that the grown TSB/Fe₃O₄ magnetic hybrid microspheres represent spherical particles with an average size of ~137 nm and a small size spread. The size and size distribution of magnetic hybrid microspheres can be controlled by a small change in the ratio of TSB and Fe³⁺ ion contents in the microsphere. TSB/Fe₃O₄ hybrid microspheres exhibit a rather high saturation magnetization (58.16 emu g^–1) and new microwave electromagnetic properties, i.e., lower (in comparison with published) dielectric losses at low frequencies; magnetic losses are increased obviously due to an increase in the TSB content. Furthermore, it is detected that magnetic hybrid microspheres absorb microwaves, and strong reflection losses in a wide frequency range are established. The effective reflection loss of–31 dB is obtained in the microwave range from 2 to 16 GHz due to TSB content variations. Wide absorption properties of microwaves along with regular spherical shape and excellent magnetic properties offer wide opportunities for various applications of TSB/Fe₃O₄ magnetic hybrid microspheres as functional materials.     

Synthesis and electrochemical properties of P2-Na<Subscript>2/3</Subscript>Ni<Subscript>1/3</Subscript>Mn<Subscript>2/3</Subscript>O<Subscript>2</Subscript>

The pure phase P2-Na_2/3Ni_1/3Mn_2/3O₂ was synthesized by a solid reaction process. The optimum calcination temperature was 850 °C. The as-prepared product delivered a capacity of 158 mAh g^?1 in the voltage range of 2–4.5 V, and there was a phase transition from P2 to O2 at about 4.2 V in the charge process. The P2 phase exhibited excellent intercalation behavior of Na ions. The reversible capacity is about 88.5 mAh g^?1 at 0.1 C in the voltage range of 2–4 V at room temperature. At an elevated temperature of 55 °C, it could remain as an excellent capacity retention at low current rates. The P2-Na_2/3Ni_1/3Mn_2/3O₂ is a potential cathode material for sodium-ion batteries.     

Ferroelectric and dielectric properties of SrBi<Subscript>4</Subscript>Ti<Subscript>4</Subscript>O<Subscript>15</Subscript> thin films grown on Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> film layer

Ferroelectric and dielectric properties of bilayered ferroelectric thin films, SrBi₄Ti₄O₁₅ grown on Bi₄Ti₃O₁₂, were investigated. The thin films were annealed at 700°C under oxygen atmosphere. The bilayered thin films were prepared on a Pt(111)/Ti/SiO₂/Si substrate by a chemical solution deposition method. The dielectric constant and dielectric loss of the bilayered thin films were 645 and 0.09, respectively, at 100 kHz. The value of remnant polarization (2P _r) measured from the ferroelectric thin film capacitors was 60.5 μC/cm² at electric field of 200 kV/cm. The remnant polarization was reduced by 22% of the initial value after 10¹⁰ switching cycles. The results showed that the ferroelectric and dielectric properties of the SrBi₄Ti₄O₁₅ on Bi₄Ti₃O₁₂ ferroelectric thin films were better than those of the SrBi₄Ti₄O₁₅ grown on a Pt-coated Si substrate suggesting that the improved properties may be due to the different nucleation and growth kinetics of SrBi₄Ti₄O₁₅ on the c-axis-oriented Bi₄Ti₃O₁₂ layer or on the Pt-coated Si substrate.     

Studies on structural and electrical properties of Mg<Subscript>0. 5+y</Subscript> (Zr<Subscript>2-y</Subscript>Fe<Subscript>y</Subscript>) <Subscript>2</Subscript> (PO<Subscript>4</Subscript>) <Subscript>3</Subscript> ceramic electrolytes

The sample of Mg_{0. 5+y} (Zr_1-y Fe_y) ₂ (PO₄) ₃ (0.0 ≤y ≤0.5) was synthesized using the sol-gel method. The structures of the samples were investigated using X-ray diffraction and Fourier transform infrared spectroscopy measurement. XRD studies showed that samples had a monoclinic structure which was iso-structured with the parent compound, Mg_0.5Zr (PO₄) ₃. The complex impedance spectroscopy was carried out in the frequency range 1–6 MHz and temperature range 303 to 773 K to study the electrical properties of the electrolytes. The substitutions of Fe³⁺ with Zr⁴⁺ in the Mg_0.5Zr (PO₄) ₃ structure was introduced as an extrainterstitial Mg²⁺ ion in the modified structured. The compound of Mg_0.5+y (Zr_1-y Fe_y)₂(PO₄)₃ with y?=?0.4 gives a maximum conductivity value of 1.25?×?10^?5 S cm^?1 at room temperature and 7.18?×?10^?5 S cm^?1 at 773 K. Charge carrier concentration, mobile ion concentration, and ion hopping rate are calculated by fitting the conductance spectra to power law variation, σ _ac (ω)?=?σ _o ? +?Aω ^α . The charge carrier concentration and mobile ion concentration increases with increase of Fe³⁺ inclusion. This implies the increase in conductivity of the compounds was due to extra interstitial Mg²⁺ ions.     

A miniature tunable TEA CO<Subscript>2</Subscript> laser using isotope <Superscript>13</Superscript>C<Superscript>16</Superscript>O<Subscript>2</Subscript> and <Superscript>12</Superscript>C<Superscript>16</Superscript>O<Subscript>2</Subscript>

A miniature tunable TEA CO₂ laser using isotope ¹³C¹⁶O₂ as the active medium is developed to extend the spectral range of CO₂ lasers for further application. The optimization of the energy parameters of the tunable TEA ¹³C¹⁶O₂ laser and the same laser using ¹²C¹⁶O₂ are studied. When a gas mixture (¹³C¹⁶O₂: N₂: He = 1: 1: 3) at a total pressure of 6.4 × 10⁴ Pa is used, the TEA ¹³C¹⁶O₂ laser of a 45-cm³ active volume obtains 51 emission lines in the [00⁰1–10⁰0] and [00⁰1–02⁰0] bands. The maximum pulse energy of the TEA ¹³C¹⁶O₂ laser is about 357 mJ. The same laser using the conventional gas mixture (¹²C¹⁶O₂: N₂: He = 1: 1: 3) at a pressure of 6.66 × 10⁴ Pa is measured to obtain 69 laser emission lines and the maximum pulse energy of laser radiation is about 409 mJ.     

Lithium diffusion in Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-based electrodes: a joint analysis of electrochemical impedance,cyclic voltammetry,pulse chronoamperometry,and chronopotentiometry data

In order to establish the mechanism and to determine the parameters of lithium transport in electrodes based on lithium-vanadium phosphate (Li₃V₂(PO₄)₃), the kinetic model was designed and experimentally tested for joint analysis of electrochemical impedance (EIS), cyclic voltammetry (CV), pulse chronoamperometry (PITT), and chronopotentiometry (GITT) data. It comprises the stages of sequential lithium-ion transfer in the surface layer and the bulk of electrode material’s particles, including accumulation of lithium in the bulk. Transfer processes at both sites are of diffusion nature and differ significantly, both by temporal (characteristic time, τ) and kinetic (diffusion coefficient, D) constants. PITT data analysis provided the following D values for the predominantly lithiated and delithiated forms of the intercalation material: 10^?9 and 3 × 10^?10 cm² s^?1, respectively, for transfer in the bulk and 10^?12 cm² s^?1 for transfer in the thin surface layer of material’s particles. D values extracted from GITT data are in consistency with those obtained from PITT: 3.5–5.8 × 10^?10 and 0.9–5 × 10^?10 cm² s^?1 (for the current and currentless mode, respectively). The D values obtained from EIS data were 5.5 × 10^?10 cm² s^?1 for lithiated (at a potential of 3.5 V) and 2.3 × 10^?9 cm² s^?1 for delithiated (at a potential 4.1 V) forms. CV evaluation gave close results: 3 × 10^?11 cm² s^?1 for anodic and 3.4 × 10^?11 cm² s^?1 for cathodic processes, respectively. The use of complex experimental measurement procedure for combined application of the EIS, PITT, and GITT methods allowed to obtain thermodynamic E,c dependence of Li₃V₂(PO₄)₃ electrode, which is not affected by polarization and heterogeneity of lithium concentration in the intercalate.     

Grain size effects on dynamics of Li-ions in Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> glass-ceramic nanocomposites

Li₃V₂(PO₄)₃ glass-ceramic nanocomposites, based on 37.5Li₂O-25V₂O₅-37.5P₂O₅ mol% glass, were successfully prepared via heat treatment (HT) process. The structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns exhibit the formation of Li₃V₂(PO₄)₃ NASICON type with monoclinic structure. The grain sizes were found to be in the range 32–56 nm. The effect of grain size on the dynamics of Li⁺ ions in these glass-ceramic nanocomposites has been studied in the frequency range of 20 Hz–1 MHz and in the temperature range of 333–373 K and analyzed by using both the conductivity and modulus formalisms. The frequency exponent obtained from the power law decreases with the increase of temperature, suggesting a weaker correlation among the Li⁺ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. The imaginary modulus spectra are broader than the Debye peak-width, but are asymmetric and distorted toward the high frequency region of the maxima. The electric modulus data have been fitted to the non-exponential Kohlrausch–Williams–Watts (KWW) function and the value of the stretched exponent β is fairly low, suggesting a higher ionic conductivity in the glass and its glass-ceramic nanocomposites. The advantages of these glass-ceramic nanocomposites as cathode materials in Li-ion batteries are shortened diffusion paths for Li⁺ ions/electrons and higher surface area of contact between cathode and electrolyte.     

Conductivity and spectroscopic studies of Li<Subscript>2</Subscript>O-V<Subscript>2</Subscript>O<Subscript>5</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses

Lithium vanadium-borate glasses with the composition of 0.3Li₂O–(0.7-x)B₂O₃–xV₂O₅ (x?=?0.3, 0.325, 0.35, 0.375, 0.4, 0.425, 0.45, and 0.475) were prepared by melt-quenching method. According to differential scanning calorimetry data, vanadium oxide acts as both glass former and glass modifier, since the thermal stability of glasses decreases with an increase in V₂O₅ concentration. Fourier transform infrared spectroscopy data show that the vibrations of [VO₄] structural units occur at V₂O₅ concentration of 45 mol%. It is established that the concentration of V⁴⁺ ions increases exponentially with the growth of vanadium oxide concentration. Direct and alternative current measurements are carried out to estimate the contribution both electronic and ionic conductivities to the value of total conductivity. It is shown that the electronic conductivity is predominant in the total one. The glass having the composition of 0.3Li₂O-0.275B₂O₃-0.475V₂O₅ shows the highest electrical conductivity that has the value of 7.4?×?10^?5 S cm^?1 at room temperature.     

The effect of LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript> on the complexation with potato starch-chitosan blend polymer electrolytes

This work examines the effect of lithium trifluoromethanesulfonate (LiCF₃SO₃) and glycerol on the conductivity and dielectric properties of potato starch-chitosan blend-based electrolytes. The electrolytes are prepared via solution cast technique. From X-ray diffraction (XRD) analysis, the blend of 50 wt.% starch and 50 wt.% chitosan is found to be the most amorphous blend. Fourier transform infrared (FTIR) spectroscopy studies show the interaction between the electrolyte materials. The room temperature conductivity of pure starch-chitosan film is found to be (2.85 ± 1.31) × 10^?10 S cm^?1. The incorporation of 45 wt.% LiCF₃SO₃ increases the conductivity to (7.65 ± 2.27) × 10^?5 S cm^?1. Further conductivity enhancement up to (1.32 ± 0.35) × 10^?3 S cm^?1 has been observed on addition of 30 wt.% glycerol. This trend in conductivity is verified by XRD and dielectric analysis. The temperature dependence of conductivity of all electrolytes are Arrhenian.     

Phase transition and electrical investigation in lithium copper pyrophosphate compound Li<Subscript>2</Subscript>CuP<Subscript>2</Subscript>O<Subscript>7</Subscript> using impedance spectroscopy

Lithium pyrophosphate compound Li₂CuP₂O₇ has been synthesized through solid state reaction method. FTIR and XRD results, realized at room temperature, indicate respectively the dominant feature of pyrophosphate anion (P₂O₇)^4? and a pure monoclinic phase with I2/a space group. Electrical and dielectric properties have been studied using impedance spectroscopy complex over a wide temperature (576–710 K) and frequency (209 Hz–1 MHz) range. From the direct and alternative conductivities (DC and AC), electrical conduction is found to be thermally activated process. The frequency-dependent AC conductivity obeys Jonscher’s universal power law σ_AC~Aω^s. The differential scanning calorimetry spectrum discloses phase transition at 622 K.     

Charge carrier mobility in crystals of the Pb<Subscript>0.67</Subscript>Cd<Subscript>0.33</Subscript>F<Subscript>2</Subscript> superionic conductor

The frequency (ν = 10^?1–10⁷ Hz) dependences σ(ν) of the conductivity of single crystals of the Pb_0.67Cd_0.33F₂ superionic conductor with the fluorite-type structure (CaF₂) in the temperature range of 132–395 K have been studied. The dependences σ(ν) have been discussed in the framework of the hopping relaxation of ionic carriers, which are mobile anions F^?. From experimental curves σ(ν), the direct-current (dc) conductivity σ_dc and the average charge carrier hopping frequency ν_h have been determined. This has made it possible to calculate the charge carrier mobility μ_mob and charge carrier concentration n _mob in these crystals. At room temperature (293 K), the electrical parameters are σ_dc = 1.6 × 10^?4 S/cm, ν_h = 2.7 × 10⁷ Hz, μ_mob = 2.0 × 10^?7 cm²/(s V), and n _mob = 5.1 × 10²¹ cm^?3.     

Thermal properties and ionic conductivity of Li<Subscript>1,3</Subscript>Ti<Subscript>1,7</Subscript>Al<Subscript>0,3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> solid electrolytes sintered by field-assisted sintering

Li_1,3Ti_0,7Al_0,3(PO₄)₃ (LATP) powder was obtained by a conventional melt-quenching method and consolidated by field-assisted sintering technology (FAST) at different temperatures. Using this technique, the samples could be sintered to relative densities in the range of 93 to 99 % depending on the sintering conditions. Ionic and thermal conductivity were measured and the results are discussed under consideration of XRD and SEM analyses. Thermal conductivity values of 2 W/mK and ionic conductivities of 4?×?10^?4 Scm^?1 at room temperature were obtained using relatively large particles and a sintering temperature of 1000 °C at an applied uniaxial pressure of 50 MPa.     

Luminescence characteristics of the Pr<Superscript>3+</Superscript> ion in SrB<Subscript>4</Subscript>O<Subscript>7</Subscript> and SrB<Subscript>6</Subscript>O<Subscript>10</Subscript>

Spectral and kinetic characteristics of the luminescence and luminescence excitation spectra of polycrystalline SrB₄O₇:Pr (1%) and SrB₆O₁₀:Pr (1%) samples are studied at 150–170 K. The samples show an intense luminescence band in the vicinity of 405 nm (¹ S ₀→¹ I ₆ transitions of Pr³⁺) and shorter wavelength bands also assigned to transitions from the ¹ S ₀ level. The main luminescence decay constant is ～2×10^?7 s. The excitation spectra of the ¹ S ₀ luminescence in these crystals are significantly different. The SrB₄O₇:Pr crystal shows three well-resolved bands at 6.14, 6.55, and 6.91 eV in the region of the 4f ²→4f ¹5d transitions and a complex structure in the region of interband transitions (7.1–20 eV), whereas the SrB₆O₁₀:Pr crystal shows a weakly structured band at 6.31 eV and no excitation in the region of the interband transitions. The physical mechanisms that may be responsible for the observed features of the spectra are discussed.     

Nanocrystalline CaCu<Subscript>3</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12</Subscript> powders prepared by egg white solution route: synthesis,characterization and its giant dielectric properties

Nanocrystalline CaCu₃Ti₄O₁₂ powders with particle sizes of 50–90 nm were synthesized by a simple method using Ca(NO₃)₂·4H₂O, Cu(NO₃)₂·4H₂O, titanium(diisoproproxide) bis(2,4-pentanedionate) and freshly extracted egg white (ovalbumin) in aqueous medium. The synthesized precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at above 400 °C. The precursor was calcined at 700 and 800 °C in air for 8 h to obtain nanocrystalline powders of CaCu₃Ti₄O₁₂. The calcined CaCu₃Ti₄O₁₂ powders were characterized by XRD, FTIR, SEM and TEM. Sintering of the powders was conducted in air at 1100 °C for 16 h. The XRD results indicated that all sintered samples have a typical perovskite CaCu₃Ti₄O₁₂ structure and a small amount of CuO, although the sintered sample of the 700 °C calcined powders contained some amount of CaTiO₃. SEM micrographs showed the average grain sizes of 12.0±7.8 and 15.5±8.9 μm for the sintered CaCu₃Ti₄O₁₂ ceramics prepared using the CaCu₃Ti₄O₁₂ powders calcined at 700 and 800 °C, respectively. The sintered samples exhibit a giant dielectric constant, ε^′ of ∼ 1.5–5×10⁴. The dielectric behavior of both samples exhibits Debye-like relaxation, and can be explained based on a Maxwell–Wagner model. PACS 77.22.Gm; 81.05.Je; 81.07.Wx; 81.20.Ev     

Microwave dielectric properties of Ba(Zn<Subscript>1/3</Subscript>Ta<Subscript>2 / 3</Subscript>)O<Subscript>3</Subscript> for application in high power waveguide window

Higher dielectric constant, low dielectric loss and good transmission characteristicshave been the goal for developing the ceramic waveguide window for high power windowapplications. The choice of materials having high k with low dielectric lossand reduced window size is key parameters to achieve maximum microwave transmissionwithout unleashing microwave dissipation. The microwave dielectric properties ofsynthesized Ba(Zn_1/3Ta_{2 /3})O₃ (BZT) ceramics have been studied for high power windowapplications. The structural studies are correlated with microwave dielectric propertiesof BZT. The maximum values of dielectric constant ?_r =30, Q ×f₀ = 102 THz and near zero temperaturecoefficient of resonance frequency were obtained for BZT ceramics sintered at thetemperature of 1550 °Cfor 4 h. The measured results are used to design a tapered transition from air filledwaveguide to narrow (reduced width and height) dielectric filled waveguide using Heckenslinear taper at a specific frequency. The simulation result shows that the lowerreflection loss is obtained for the tapered transition of the narrow BZT window ascompared to the standard waveguide BZT window. The return loss of –34 dB is obtained forS-bandwaveguide window with a bandwidth of 675 MHz. The return loss observed in the narrow BZTwindow is –46 dB with a bandwidth of 570 MHz at a center frequency of 3.63 GHz. Most ofthe disadvantages in conventional windows will be rectified using the design of the tapertransion employing narrow waveguide window in high power applications.     

Synthesis of plate-like Li<Subscript>3</Subscript>PS<Subscript>4</Subscript> solid electrolyte via liquid-phase shaking for all-solid-state lithium batteries

The precursor of plate-like Li₃PS₄ solid electrolyte (75Li₂S?25P₂S₅, SE (LS)), about 3 μm in length, 500 nm in width, and 100–200 nm in thickness, was successfully prepared from Li₂S and P₂S₅ using ethyl propionate (EP) as a synthetic medium via liquid-phase shaking. Upon evacuating at 170 °C, the precursor decomposed to SE (LS), which exhibited ionic conductivity of about 2.0 × 10^?4 Scm^?1 at room temperature. SEM observation revealed that the SE (LS) thus obtained had plate-like morphology with dimension of 3 μm in length, 500 nm in width, and 100–200 nm in thickness. Owing to the nanosized SE (LS), an all-solid-state half-cell using composite anode consisting of 90 wt% LiNi_1/3Mn_1/3Co_1/3O₂ (NMC) and 10 wt% SE (LS) delivered a high capacity up to 130 mAhg^?1(NMC) at the first discharge.     

Linear and nonlinear optical spectroscopy of gadolinium iron borate GdFe<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>

The optical spectra and the second-harmonic generation (SHG) are studied in a noncentrosymmetric GdFe₃(BO₃)₄ magnet. In the region of weak absorption (α～20–400 cm^?1) below ～3 eV, three absorption bands are distinguished, which can be unambiguously assigned to forbidden electronic transitions from the ground ⁶A₁ state of the Fe³⁺ ion to its excited states ⁴T₁(～1.4 eV), ⁴T₂(～2 eV), and ⁴A₁, ⁴E(～2.8 eV). Intense absorption begins in the region above 3 eV (α～2–4×10⁵ cm^?1), where two bands at ～4.0 and 4.8 eV are observed, which are caused by allowed electric dipole charge-transfer transitions. The spectral features of SHG in the 1.2–3.0-eV region are explained by a change in the SHG efficiency caused by a change in the phase mismatch. It is shown that in the weak absorption region, phase matching can be achieved for SHG.     

Optical and magnetooptical properties of CoFeB/SiO<Subscript>2</Subscript> and CoFeZr/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> granular magnetic nanostructures

The optical and magnetooptical properties of the new granular nanocomposites (CoFeB)/(SiO₂) and (CoFeZr)/(Al₂O₃), which are grains of amorphous ferromagnetic alloys embedded in dielectric matrices, have been studied. The dependence of the optical, magnetooptical, and magnetic properties of the nanocomposites on their qualitative and quantitative composition, as well as on the conditions of their preparation, was investigated. Spectra of the dielectric functions ε = ε₁ ? iε₂ were obtained by the ellipsometric method in the range 0.6–5.4 eV. Above 4.2 eV, the absorption coefficient of the (CoFeB)/(SiO₂) composites was found to be close to zero for all magnetic-grain concentrations. The polar Kerr effect measured at a photon energy of 1.96 eV in dc magnetic fields of up to 15 kOe reaches values as high as 0.25°–0.3° for these nanocomposites and depends only weakly on the conditions of preparation. On the other hand, the (CoFeZr)/(Al₂O₃) nanostructures reveal a considerable difference in the concentration dependences of the Kerr effect between samples prepared in a dc magnetic field and in zero field.