Electrical properties of LiBBaTe glass doped with Nd2O3

The dc and ac electrical conductivity of barium tellurite borate glass doped with Nd₂O₃ in the composition 50 B₂O₃- (20-X) BaO- 20TeO₂ 10 LiF or Li₂O where x = 0.5, 1, 1.5 and 2 Nd₂O₃ were measured in the temperature range 303–648 K and in the frequency range 0.1–100 kHz. The dc and ac conductivities values increase, whereas the activation energy of conductivities decreases with increasing Nd₂O₃ content in the glasses containing LiF and by the replacement of LiF by Li₂O the conductivity was found to decrease with addition of Nd₂O₃. The electrical conduction has been observed to be due to small polaron hopping at high temperatures. The frequency dependence of the ac conductivity follows the power law σ_AC (ω) = A ω^s. The frequency exponent (s) values (in the range 0.94 and 0.33) decreases with increasing temperature. The dielectric constant and dielectric loss increased with increasing temperature and decreased with increase in frequency for all glasses studied. In LiF glasses, it is observed that, the values of ?^\ and tan δ are observed to increase with the addition of Nd₂O₃ whereas they decrease in the glasses containing Li₂O. The electrical modulus formalism has been used for studying electrical relaxation behavior in studied glasses. It is for first time that the Nd₂O₃ doped barium tellurite borate glasses have been investigated for dc and ac conductivities and dielectric properties over a wide range of frequency and temperature.     

Detection of up-conversion in nano-structure BaTiO<Subscript>3</Subscript> co-doped with Er<Superscript>3+</Superscript> and Yb<Superscript>3+</Superscript> ions

Nano-structure pure barium titanate BaTiO₃ (BT) and (BT) co-doped with constant concentration of Er³⁺ ions and different concentrations of Yb³⁺ ions were prepared using sol–gel method. XRD results confirmed that the pure sample was found to crystallize in tetragonal phase by sintering at 750 °C for 1 h. All major peaks corresponding to perovskite BT phase appeared. Efficient infrared-to-visible up-conversion is reported in the doped samples. The conversion process and results in the generation of visible emissions are discussed. Up-conversion efficiency for red emission predominates in doped samples. Results illustrate the large potential of this class of materials for photonic applications in optoelectronics devices.     

Microwave frequency effects on dielectric properties of some common solvents and on microwave-assisted syntheses: 2-Allylphenol and the C12–C2–C12 Gemini surfactant

Microwave radiation emitted at a frequency of 915 MHz and 5.8 GHz from a newly fabricated single-mode resonance microwave apparatus is herein proposed for use in microwave-assisted organic syntheses. The usefulness of 5.8-GHz microwaves is demonstrated by the solvent-free synthesis of 2-allylphenol through a Claisen rearrangement process, and by the synthesis of the C₁₂–C₂–C₁₂ Gemini surfactant in ethanol solvent undertaken to verify the usefulness of the 915-MHz frequency. These two model reactions have shown the advantage of these two microwave frequencies in that the observed efficiencies were greater than when employing the more commonly used 2.45-GHz microwaves. Dielectric parameters (dissipation factor: tan δ, dielectric constant: ε′, and dielectric loss: ε′′) have also been assessed for water and 22 common organic solvents typically used in organic syntheses, together with the temperature dependence of the dielectric parameters. Temperature–time profiles have been determined and rates of increase of temperature computed. The 5.8-GHz microwaves were effective in heating non-polar solvents, while the 915-MHz microwave frequency was most suitable for heating the alcohols.     

(Ba<Subscript>0.93</Subscript>Nd<Subscript>0.07</Subscript>)TiO<Subscript>3</Subscript> thin films prepared by sol–gel method as a potential dielectric resonator antenna application

In this paper, we report the application of Neodymium (Nd) doped barium titanate thin films (Ba_1-xNd_x) TiO₃ with x = 0 and 0.07 as dielectric resonator antenna. The films were prepared using the sol–gel method and dip-coating technique. Barium acetate, titanium (IV) isopropoxide and neodymium (III) acetate hydrate were used as precursors while glacial acetic acid and acetylacetone were used as solvents. Si wafers were used as a substrate with dipping times varying from 10, 30, and 50 s. The 0.07 films were >800 nm thick and crystallized after being annealed at 800°C for 30 min. The films were tested as dielectric resonator antenna. It was found that, on the actual antenna circuit, the resonant frequency decreased as the (Ba_0.93Nd_0.07) TiO₃ films thickness increased (from 0.8379, to 5.4525 μm). All samples resonate in the range of 8.68–8.83 GHz with quasi omni-directional radiation patterns.     

Effect of ZnO on sintering and microwave dielectric properties of 0.5CaTiO3-0.5 (Li0.5La0.5) TiO3 ceramics

The novel calcium titanate-lithium lanthanum titanate doped with zinc oxide (0.10, 0.30, and 0.50 mol. %) ceramic samples were prepared by solid-state reaction route. The phase formation, microstructure, densification, and microwave dielectric properties were investigated. It was found that the doping with zinc oxide led to a decrease in sintering temperature by 25 ^oC as compared with pure calcium titanate lithium lanthanum titanate due to the liquid phase effect. Also, the calcium titanate lithium lanthanum titanate (10ZCTLLT&30ZCTLLT)) doped with lower zinc oxide (0.10 and 0.30 mol. %) led to higher densification parameter. This was followed by increasing the zinc oxide doping up to (0.50 mol. %) which resulted in a decrease in densification and microwave dielectric properties which may be attributed to increase in porosity and grain growth upon the evaporation of zinc and oxygen vacancy. This led to the increase in dielectric loss (≈10 × 10^?4) value with 50ZCTLLT. Hence, the best result of microwave dielectric characteristics was obtained for 0.5CaTiO₃–0.5(Li_0.5La_0.5)TiO₃ with (0.10 and 0.30 mol. % ZnO) 10ZCTLLT and 30ZCTLLT ceramic samples sintered at 1175 ^oC/2h, with low dielectric constant (ε_r) = 4.4–10.5, very low dielectric loss = 1.07-2.23 × 10^?4 and high quality factor (Q x ?) ≈59-55 × 10⁴ at 8 GHz. Consequently, they can be used not only in wireless satellite communications technology but also can be used in the fifth-generation telecommunication 5G technology construction.     

Dielectric and optical properties of BaTiO<Subscript>3</Subscript> thin films prepared by low-temperature process

Barium titanate (BaTiO₃) thin films have been prepared by low temperature processing on Pt/Ti/SiO₂/Si substrates using sol-gel-hydrothermal (SGHT) technique, which combined the conventional sol-gel process and hydrothermal method. X-ray diffraction analysis showed that the barium titanate thin films are polycrystalline. As-reacted barium titanate films grown on Pt(111)/Ti/SiO₂/Si(100) substrates had a dielectric constant (ε) and loss tangent (tanδ) of 80 and 0.05 at 1 MHz, respectively. The optical constants including refractive index n, extinction coefficient k, and absorption coefficient α of the barium titanate thin films in the wavelength range of 2.5–12.6 μm were obtained by infrared spectroscopic ellipsometry.     

Study on conductivity and dielectric behavior of chemically synthesized polypyrrol dodecylbenzene sulfonic acid blended with poly(methyl methacrylate)

Polypyrrole (PPy) doped with dodecylbenzene sulfonic acid was synthesized and was blended with compatible polymer PMMA in chloroform. Flexible and free-standing films with compositions PPy: PMMA = 10: 90, 20: 80, 30: 70, and 50: 50 were obtained. The percentage of crystallinity and particle size of synthesized polymers were estimated from X-rays diffraction studies. Scanning Electron Micrographs showed that phase separation was observed and compatibility of the mixture decreased with increase of PMMA content. The dielectric measurements were performed in the frequency range 0.1 kHz–1 MHz in temperature range 303–473 K. The frequency dependent conductivity (σ_ac) obeyed a power law of frequency with an exponent s < 1. Electric modulus formalism exhibits a peak in frequency. The peak of conductivity relaxation shifted towards higher frequencies and the magnitude of relaxation decreased with the increase of PMMA content in the composites.     

In-situ fabrication of barium titanate@polyvinyl pyrrolidone in polyvinylidene fluoride polymer nanocomposites for dielectric capacitor applications

We have demonstrated an in situ route to design barium titanate (BT)@polyvinyl pyrrolidone (PVP) nanoparticles (NPs) in PVP/polyvinylidene fluoride (PVDF) blends. Thus, the PVP simultaneously acted as a linker and a part of the polymer matrix. We have hydrothermally synthesized the tetragonal phase of BT NPs (~150 nm). The BT NPs content was varied from 0 to 15 vol%. The resulting polymer nanocomposites generated enormous interfaces because of homogeneously dispersed BT@PVP NPs. Furthermore, the PVP simultaneously tailored the interfacial properties surrounding the BT NPs and bulk of the polymer matrix. Therefore, we achieved an enhanced maximum polarization (P_max) and energy density (U_d) of 27.9 μC cm⁻² and 13.4 J cm⁻³ (2261 kV cm⁻¹), respectively, at 7.5 vol% BT NPs loadings. At the same time, PVP/PVDF blends showed P_max and U_d of only 3.9 μC cm⁻² and 4.6 J cm⁻³ (3369 kV cm⁻¹), respectively. This simple approach of in situ nanomaterials modification will lead to development of low-cost and time-efficient dielectric capacitors.     

Chemical Preparation of Ferroelectric Mesoporous Barium Titanate Thin Films: Drastic Enhancement of Curie Temperature Induced by Mesopore‐Derived Strain

Mesoporous barium titanate (BT) thin films are synthesized by a surfactant‐assisted sol–gel method. The obtained mesoporous BT thin films show enhanced ferroelectricity due to the effective strains induced by mesopores. The Curie temperature (T_c) of the mesoporous BT reaches approximately 470 °C.     

PVDF/PMMA dielectric films with notably decreased dielectric loss and enhanced high‐temperature tolerance

Polymer dielectrics generally have comparatively low dielectric constant, operating temperatures, and/or high dielectric loss, which limits their uses especially in harsh environment. In this article, a novel trilayered nanocomposite film (TNF) was constructed via solution‐casting and, subsequently, hot‐pressing process, which was composed of two outer layers of polyvinylidene fluoride (PVDF, high dielectric constant) and a middle layer of polymethyl methacrylate (PMMA, high glass transition temperature, T_g). The two outer layers of TNF were filled with barium strontium titanate nanoparticles to further increase the dielectric constant of PVDF. The PMMA in the middle layer was used to largely suppress the dielectric loss and simultaneously improve the temperature tolerance of TNF. Results show that the introduction of PMMA induced oriented crystal formation in the interface regions between PVDF and PMMA components. Moreover, most of the impurity ions were dramatically immobilized by partly oriented α crystals and high T_g PMMA layer until the temperature exceeded 120 °C. Therefore, the TNFs showed a high‐temperature tolerance and notably decreased loss, which are promising for widespread energy storage applications where harsh working conditions are present. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1043–1052     

Barium Titanate-reinforced Acrylonitrile-Butadiene Rubber: Synergy Effect of Carbon-based Secondary Filler

Acrylonitrile rubber(NBR) composites filled with barium titanate(BT) were prepared using an internal mixer and a two-roll mill. Also, a secondary filler, namely carbon nanotubes(CNT), was added in order to find a potential synergistic blend ratio of BT and CNT. The cure characteristics, tensile and dielectric properties(dielectric constant and dielectric loss) of the composites were determined. It was found that NBR/BT composites with CNT secondary filler, at a proper BT:CNT ratio, exhibited shorter scorch time(t_(s1)) and cure time(t_(c90)) together with superior tensile properties and reinforcement efficiency, relative to the one with only the primary filler. In addition, the NBR/BT-CNT composite with 80 phr BT and 1-2 phr CNT had dielectric constant of 100-500, dielectric loss of 12-100 and electrical conductivity below 10~(-4) S/m together with high thermal stability. Thus, with a proper BT:CNT mix and filler loading, we can produce mechanically superior rubber composites that are easy to process and low-cost, for flexible dielectric materials application.     

Effect of the Different Sr Dopant Contents on NiO Ceramic

Sr - doped NiO ceramic was studied. The effect of composition variation of Ni_(1-x)Sr_xO where x = 0, 0.01, 0.02, 0.03, 0.05 and 0.10 mole % was prepared by using solid state method. The calcination temperature used at 950 °C for 4 hours and the sintering temperature used at 1200 °C for 3 hours. The results depict the microstructures increase in grains size (0.43 - 3.30 μm) by increase of Sr dopant contents. The density and porosity testing support the result of microstructures analysis. The larger grains size led to increase in density and lower in porosity. The dielectric properties is observed in a wide frequency range of (1 - 1 000 MHz). The increase of dielectric constant is associated with the decrease of dielectric loss. The optimum composition was obtained for the x = 0.03 mole % sample with highest dielectric constant (3.24 x 10³) and lowest dielectric loss (1.42) at 1 MHz.     

Electrical,dielectric and pyroelectric behavior of neodymium substituted barium zirconium titanate

Neodymium (Nd) substituted barium zirconium titanate with nominal composition (Ba_1−xNd_x)(Zr_0.52Ti_0.48)O₃ [x = 0.1, and 0.2] were synthesized using solid state reaction method. X-ray analysis confirmed the formation of perovskite structure along with minor pyroclore phase of neodymium. The change in grain size revealed the influence of Nd-ions on the microstructure. The sintered samples exhibited negative temperature coefficient of resistance (NTCR) and superior semiconducting behavior. Addition of Nd³⁺varies the room temperature resistivity of Ba(Zr_0.52Ti_0.48)O₃. As the concentration of Nd-ion increased, the value of temperature dependent dielectric constant decreased whereas the Curie temperature of the ceramics shifted toward higher temperature side showing diffuse phase transition. This is attributed to decrease in average grain size. Temperature dependent pyroelectric current exhibited combination of primary and secondary pyroelectric effect.     

Structural,optical and dielectric relaxor properties of neodymium doped cubic perovskite (Ba1−xNd2x/3)(Zr0.3Ti0.7)O3

Neodymium doped Barium Zirconate Titanate (Ba_1−xNd_2x/3)(Zr_0.3Ti_0.7)O₃ (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10) ceramics were prepared using the solid state reaction route. Structural characterizations of the materials were done by using X-ray diffraction and Raman spectroscopy. XRD study suggested that all the compositions were of single phase cubic perovskite structure with space group Pm-3m while Raman spectra revealed that the replacement of the Ba²⁺ ions by Nd³⁺ ions significantly reduced the intensity of the Raman active modes and shifted them towards higher energy side. Room temperature optical property was analyzed by photoluminescence spectroscopy, which confirmed formation of shallow defects in the band gap. Photoluminescence property was attributed to the presence of polar [TiO₆] distorted clusters in the globally cubic matrix. As a result PL emission spectra of these materials were found to belong to violet–blue regions. Microstructural study of sintered pellets revealed that the grain sizes increase with increase in doping concentration. The temperature dependence of the dielectric properties was investigated in the frequency range 1 kHz to 1 MHz. The broadening in the dielectric constant peak around the phase transition temperature and shifting of the temperature maximum towards higher temperatures with increase in frequency indicated a relaxor type of behavior.     

Dielectric behavior and impedance analysis of lead-free CuO doped (Na0.50K0.50)0.95(Li0.05Sb0.05Nb0.95)O3 ceramics

Pure (Na_0.50K_0.50)_0.95(Li_0.05Sb_0.05Nb_0.95)O₃ (NKNLS) and CuO doped NKNLS perovskite structured ferroelectric ceramics were prepared by the solid-state reaction method. x wt% of CuO (x = 0.2–0.8 wt%) was added in the NKNLS ceramics. X-ray diffraction patterns indicate that single phase was formed for pure NKNLS while a small amount of second phase (K₆Li₄Nb₁₀O₃₀ ∼ 3%) was present in Cu²⁺ doped NKNLS ceramics. Dielectric anomalies around the temperatures of 120 °C and 350 °C have been identified as the ferroelectric–paraelectric transition (orthorhombic to tetragonal and tetragonal to cubic) temperatures for pure NKNLS compound. The electrical behavior of the ceramics was studied by impedance study in the high temperature range. Impedance analysis has shown the grain and grain boundary contribution using an equivalent circuit model. The impedance response in pure and Cu²⁺ doped NKNLS ceramics could be resolved into two contributions, associated with the bulk (∼grains) and the grain boundaries. From the conductivity studies, it is found that activation energies are strongly frequency dependent. The activation energy obtained from dielectric relaxation data may be attributed to oxygen ion vacancies.     

Sol-gel synthesis of cerium dioxide nanoparticles coated with stimuli-responsive components and the application for conversion of <Emphasis Type="SmallCaps">d-</Emphasis>(−)-fructose into platform molecules

Barium zirconium titanate (Ba(Zr _x Ti_1?x)O₃, BZT) super smooth thin films are synthesized through modified sol-gel dip coating route on fluorine-doped tin oxide substrates with a suitably low calcination temperature. The Fourier tranformed infrared spectroscopy proves that impurities and starting materials are completely removed in the calcination process. Crystallographic phases of the samples are identified by the X-ray diffractometry and confirms that all samples are crystallized into a single perovskite phase. Introducing zirconium into the structure causes a reduction in dielectric constant of barium titanate. The optical properties of the films are also investigated. The results indicate that all samples are highly transparent and zirconium reduces the absorption coefficient. Moreover, the band gap energy of barium titanate increases when doped with zirconium and the highest band gap energy of about 3.71?eV along with the lowest dielectric constant of 850 at frequency of 100?kHz are obtained in 15 at.% zirconium-doped sample.

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Liquid-phase synthesis of barium acetatotitanyl and barium oxalatotitanyl as intermediates for preparing nanosized barium titanate

Liquid-phase methods (an oxalate process in aqueous solution and a semialkoxide sol-gel process in anhydrous acetic acid) were used to prepare barium acetatotitanyl (BAT) and barium oxalatotitanyl (BOT), which are potential fillers for electrorheological liquids, and to prepare barium titanate during heat treatment of the aforementioned intermediates at 1200°C. The materials were characterized using electron microscopy, FTIR spectroscopy, and thermal analysis. The particle size was 80 to 100 nm for BAT powders and 20 to 50 nm for BOT powders. X-ray spectra of the powders dried at 120°C contain reflections from a barium titanate phase. The dielectric spectra of the materials synthesized were studied for suspensions in PMS-20 silicone oil over the frequency range from 25 to 10⁶ Hz up to 4 kV/mm. The dielectric parameters of BOT suspensions decrease hyperbolically with rising alternate current frequency, whereas BAT suspensions give rise to a relaxation dielectric spectrum with relaxation times on the order of 10⁻³ s.     

Temperature dependence of electron spin resonance in CaCu3Ti4O12 substituted with transition metal elements

The temperature dependence of the electron spin resonance (ESR) spectrum of copper in CaCu₃Ti₄O₁₂ (CCTO) polycrystalline samples doped with transition metal elements Mn, Fe, Ni is reported. The frequency dependence of the dielectric constant of the sample is also reported at room temperature. While the dielectric constant of undoped CCTO samples reaches ～10,000, it is found one hundred times lower in samples doped with only 0.5 or 1% of Mn or Fe. Copper is confirmed to give a g = 2.14 signal at room temperature for substituted and unsubstituted samples. Below the antiferromagnetic transition that occurs near 25 K, the signal is found shifted down to low fields for all samples. However the downshift is 10–20 times more important in Mn and Fe-doped samples compared to undoped or Ni-doped CCTO. ESR results in an undoped CCTO thin film grown by pulse laser deposition are also reported. While in the low-temperature antiferromagnetic phase the spectrum is multi-line and magnetic-field-orientation-dependent, it reduces to a narrow single line, independent of the orientation of the magnetic field, in the upper paramagnetic phase, similar to the undoped polycrystalline sample. All doped samples display much broader response in the upper phase. The results are discussed within the framework of the relationship between the high effective dielectric constant and the electrical conductivity of CCTO bulk.