Journal of Electroceramics最新文献

The substitution of Dy³⁺ ions in the M-type hexaferrite structure has been successfully synthesized by sol-gel combustion method according to the formula SrDy_xFe_12-xO₁₉ (x = 0.0, 0.08, 0.16, 0.24, 0.32, and 0.40). The XRD analysis confirmed the formation of single-phase M-type hexagonal structures up to x = 0.24 compositions. The average crystallite size for the SrDy_xFe_12-xO₁₉ samples ranges from 90.64 to 290.04 nm, whereas the value of the lattice parameters 'a' and 'c' vary from 5.8590 - 5.8879 Å and 22.9675 - 23.0761 Å, respectively. Scanning electron microscopy (SEM) was used for morphological analysis. Due to ceasing effect of polarization, the dielectric constant decreases in the higher frequencies. The SrDy_xFe_12-xO₁₉ hexaferrites exhibit non-Debye type dielectric relaxation behavior confirmed by complex impedance spectroscopy (CIS) investigation. The SrDy_xFe_12-xO₁₉ samples can be utilized as a promising material for various device applications due to a decrease in dielectric loss and an increase in dielectric constant with increasing Dy³⁺ ions concentration.

Barium titanate ceramics with A- site and B-site substitutions are intriguing alternative to lead-based Pb (Zr, Ti) O₃ (PZT) because of its comparable properties to soft-PZTs. In this paper, (Ba_xCa_1-xSn_0.09 Ti_0.91) O₃ (x = 0.0525, 0.0575, 0.060) ceramics are prepared using a solid-state reaction technique followed by microwave sintering at 1350 °C for 30 minutes. Structural and electrical properties are investigated. X -ray diffraction shows that the compositions exhibit a tetragonal crystal structure having P4mm symmetry. Temperature dependent dielectric constant measurements in the temperature range of 25 °C to 120 °C shows high dielectric constant of 26250 at 40kHz for BCST ceramics with x=0.0525 and the Curie temperature T_c increases with Ca concentration. The results of dielectric measurements as a function of frequency are also reported. The dielectric loss (tan δ) values in the temperature range 25 °C to 120 °C are observed to be less than 0.03, for all BCST ceramics. The AC conductivity, impedance spectroscopy studies and the conduction mechanism on the basis of Arrhenius plot are discussed in the above-mentioned temperature range.

In order to improve the energy storage performance of Bi-based lead-free ceramics in dielectric capacitors, K_0.5Bi_0.5TiO₃ is doped into Bi_0.5Na_0.5TiO₃-Bi_0.2Sr_0.7TiO₃ (NBT-SBT) ceramics. We find that NBT-SBT-xK_0.5Bi_0.5TiO₃ (NBT-SBT-xBKT, x=0, 0.02, 0.03, 0.05 and 0.08) ceramic sheets maintain the perfect pure perovskite structures and show the character of relaxor ferroelectrics, indicating that the doped K⁺ ions smoothly infiltrate into the host lattice of binary system NBT-SBT ceramics and then disturb the long-range order of ferroelectric material and cause the lattice deformation in NBT-SBT. As such, the NBT-SBT-0.03BKT ceramic sample obtains dielectric constant (ε_r) of 1736, dielectric loss (tanδ) of 0.05, and energy storage efficiency (η) of 70.7%, respectively. More strikingly, NBT-SBT-xBKT ceramics exhibit excellent temperature stability, which helps to store energy at high temperatures. This paper can provide an effective method for manufacturing ceramic based capacitors with high energy storage property.

In this research work, the microwave dielectric and shielding properties of (0.96M_xMg_1-xTiO₃ – 0.04SrTiO₃) (M = 0, x = 0.0; M = Zn, x = 0.05; M = Zn, x = 0.075; M = Co, x = 0.05; and M = Co, x = 0.075) solid solutions were studied in a Ku and K frequency band using a vector network analyzer. The samples were prepared via the auto-ignition combustion method and sintered at a temperature of 1200°C for 4 hours. An investigation of the shielding properties revealed that these materials' shielding effectiveness (SE) varied as a function of composition and frequency. The shielding analysis exhibited that compositions (M = Zn, x = 0.05) and (M = Co, x = 0.05) showed maximum shielding effectiveness by providing SE > 10 dB for a bandwidth of 2.72 GHz and 4.48 GHz, respectively. The highest SE was observed for composition (M = Co, x = 0.05) at a frequency of 17.21 GHz with SE~31.05 dB corresponding to a restriction of 99.81 % of incident power. These compositions are proposed as effective shielding materials for electromagnetic radiations in Ku-band and K-band.

The reaction sintering, without calcination and following re-grinding, has been paid increasing attention. Non - stoichiometric Li₂Mg₃Sn_1 − xO₆ (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10) ceramics were successfully gained through reaction sintering process in the study, and its phase composition, morphology and dielectric characteristics were studied. This XRD patterns of Li₂Mg₃Sn_1 − xO₆ samples prepared after sintering at 1,305 ℃ for 6 h indicates that green bodies are mainly composed of Li₂Mg₃SnO₆ phase, accompanied by the second phase of Mg₂SnO₄. A host of pores, elliptic - like grains and wrinkle - like grains were visibly observed from the SEM images of Li₂Mg₃Sn_1 − xO₆ ceramics, which is because of the severe volatilization of Li elements at high temperature. The apparent density, relative permittivity, quality factor and temperature coefficient of resonant frequency of samples will be devastate owing to porous morphology and Mg₂SnO₄ phase to a large extent. Finally, when x = 0.08, Li₂Mg₃Sn_0.92O₆ ceramics have optimal dielectric performances: ε_r = 9.133, Q×f = 55,429 GHz, τ_f = -36.1 ppm/℃.

We describe the development and characterization of a stretchy and resilient micro-strip antenna made from a nanocomposite of polydimethylsiloxane (PDMS) and bentonite clay loaded with silver, copper, and graphene nanoparticles. The physical, mechanical, and thermal characteristics of the nanocomposite were extensively evaluated in relation to the different nanomaterial loading into the PDMS. This has included UV-Vis spectroscopy, X-ray diffraction, and other techniques in addition to tensile and flexural tests, rheological analysis, thermogravimetric analysis, scanning and transmission electron microscopy, dynamic viscosity study, and ion coupled plasma. The conductivity of the fabricated micro-strip antennas was assessed using electrochemical impedance spectroscopy, and the antenna pattern was suitable for usage in RF equipment for cutting-edge applications like military, sensing, and space.

Oxygen non-stoichiometry profoundly impacts the electrical, magnetic, and catalytic properties of metal oxide. Limited by the low mass and volume of thin oxide films, conventional quantification methods, such as thermogravimetry, are not directly applicable. While chemical capacitance has been successfully applied to monitor oxygen non-stoichiometry in thin oxide films, detailed a-priori understanding of the defect chemistry is often very helpful in its interpretation. In this study, changes in non-stoichiometry in Pr doped CeO₂ (PCO) thin films are measured by coulometric titration. I-V titration measurements are performed on electrochemical cells, over the temperature range from 550 to 700 ℃, oxygen partial pressure range from 10^-4 to 0.21 atm, and bias range of -50 mV to 50 mV, to extract changes in stoichiometry. The results agree well with values obtained by chemical capacitance, demonstrating the utility in applying coulometric titration to investigate oxygen non-stoichiometry in oxide thin films.

In the present work, tackle the two issues with one single activity resource that strategy has followed. The organic dye methyl orange (MO) and drug ciprofloxacin (CIP) have been effectively degraded by the synthesized ZnO@CuO under visible light irradiation. The hexagonal structured zinc oxide (ZnO), monoclinic structured copper oxide (CuO) and the mixed phase of ZnO@CuO has been prepared by the hydrothermal method. The structural characterization of prepared materials has been analyzed by powder X-ray diffraction (P-XRD) and the Rietveld refinement technique. The surface morphology of synthesized materials has been measured by scanning electron microscope characterization. The luminescence performance of prepared materials has studied by photoluminescence (PL) characterization. The photocatalytic results suggest that the ZnO@CuO composite is the effective candidate of degradation of ciprofloxacin antibiotic drug and methyl orange dye. From the results, ZnO@CuO revealed excellent photocatalytic behavior for CIP and MO degradation under stimulated sun light irradiation with the efficiency of above 95%. In addition, the optimum parameters were analyzed to the degradation process. This type of affordable photocatalyst gives a new beginning for further research studies. In addition, the electron density distribution analysis of synthesized materials has been studied.

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In this work, H₃BO₃ and Bi₂O₃ with the ratio 3:2 were melted at 750 °C and then quenched in water to produce B-Bi-O frit, which was sintered and co-doped with TiO₂-0.60Nb₂O₅-0.50ZnO varistor ceramics. It is found that B-Bi-O frit can reduce the sintering temperature and improve the electrical properties of TiO₂ ceramics. The best comprehensive electrical properties with the nonlinear coefficient up to 8.9, the breakdown voltage down to 4.92 V/mm, the relative dielectric constant of 4.47*10⁵ and the leakage current of 0.102 mA are achieved by sintering the ceramics doped with 3 wt% B-Bi-O frit at 1400 °C. XRD analysis shows that B-Bi-O frit is an amorphous phase, and no second phase can be found in ceramics after the frit is doped. SEM morphologies display that B-Bi-O frit is beneficial to decrease the porosity while increase the grain size, and EDS mapping further presents no elements segregate on the grain boundary. XPS spectra demonstrate the coexistence of Ti³⁺ ions, Ti⁴⁺ ions and oxygen vacancies in TiO₂ ceramics. As a result, it can be concluded that the enhancement of the electrical properties of TiO₂ ceramics is mainly attributed to the following aspects: on the one hand, B-Bi-O frit helps to produce liquid phase sintering, which would reduce the porosity while increase grain size and promote solid solution of Nb₂O₅ and ZnO in TiO₂ ceramic. On the other hand, B and Bi elements can also act as acceptor dopants in TiO₂ ceramic to further promote grain semi-conductivity and increase grain boundary barrier height.

La_0.6Sr_0.4FeO₃ ceramic was elaborated by solid-state route. Preliminary room-temperature structural analysis evidences the sample formation in the orthorhombic structure and its phase purity. Electrical properties of the studied ceramic have been investigated according to dielectric measurements in the frequency range 10^–1 - 10⁶ Hz and the temperature range 93 - 313 K. Electrical conductivity curves exhibit a step-like behavior, at low temperatures, attributed to grain boundaries and grain contributions which are well described by the two Jonscher equations. The grains conduction mechanism is consistent with the thermally activated hopping of small polaron (SPH). Whereas, this mechanism is no longer satisfied for grain boundaries conduction mechanism at lower temperatures. Indeed, this latter is governed by the variable range hopping (VRH) model. This electrical conductivity analysis is further confirmed by the complex impedance formalism according to the obtained activation energies. Analysis of Nyquist plots at low temperatures has evidenced the presence of two grain boundaries effects attributed to the heterogeneous structure of La_0.6Sr_0.4FeO₃ grain boundary according to the morphological analysis_. Such characteristic may be at the origin of the grain boundaries electrical conductivity mechanism change at low temperatures.