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Structural and optoelectronic properties of Ce-Al2O3 nanoparticles prepared by sol-gel precursors
摘要： Pure and Ce-doped Al2O3 nanoparticles (NPs) were synthesized in different cerium percentages of 1%, 2%, and 3% by cerium chloride and aluminum nitrate precursors in the presence of powerful reducing agent-NaBH4 and CTAB stabilizers using sol-gel method. To examine the crystal, morphological, optical, and electronic properties, the XRD, FESEM, TEM, FTIR, UV-DRS, and PL analyses were used for the heated samples in 1000 °C for 4 hours. The XRD analysis indicated that the pure sample has γ, δ and θ phases, and the structure remained unchanged when Ce impurity was increased. The EDS analysis showed that the percentage of Al element was 47.40 wt% in the pure sample and that it increased to 53.83 wt% for 1% doped sample increasing Al ions in tetrahedral and octahedral sites of alumina through increasing Ce impurities. The TEM results revealed the sphere-like particles with mean particle size of 26 nm in diameter at a 3% level of impurity. The FTIR result showed that an increase in AlO4 adsorption peak in 821 cm-1 compared to AlO6 adsorption peak in 619 cm-1 was due to the dominance of vibrating bonds of tetrahedral sites rather than octahedral sites in alumina. The optical UV-DRS analysis also demonstrated the redshift configuration in a sample by increasing Ce dopant and reducing energy bandgap from 4.10 to 3.26 eV for pure and 3% Ce-doped Al2O3 NPs, respectively. Finally, the photoluminescence (PL) results indicated that increasing Ce dopant reduced electron-hole recombination leading to an increase in photocatalytic activity.
关键词： Chemical Synthesis,Cerium dopant,Sol-gel,Ceramics,Al2O3 NPs
更新于2025-09-04 15:30:14
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Electrical characteristics of PbO–CaO–TiO2–SiO2–B2O3 glass ceramics doped with germanium
摘要： Various glass samples in the compound 55[(PbxCa1?x)O?TiO2]-44[2SiO2?B2O3]-1Ge (0 ≤ x ≤ 0.7) were fabricated by using the melt-quenching technique and their glass ceramics (GC) were obtained by controlled crystallization of the glass samples. The identification of phase and crystal structure with measurement of cell parameters was carried out using X-ray diffractometer (XRD). XRD results revealed the presence of the single phase formation of rutile (TiO2). The surface morphology of the synthesized GC samples was evaluated using a scanning electron microscope (SEM). The electrical behaviour of three selected GC samples with x = 0.0, 0.3 and 0.7 was being widely studied using impedance and immittance spectroscopy. The lead free GC sample, x = 0.0 possesses a high dielectric constant, 91,252 at low frequency (50 Hz) and high temperature (500 °C) due to space charge polarization that was ascertained by impedance spectroscopy of the tested samples. The fitting of impedance spectra with a modelled equivalent circuit was performed and different values of resistance and capacitance were calculated.
关键词： Dielectric constant,Rutile TiO2,Glass ceramics,Impedance spectroscopy,Space charge polarization
更新于2025-09-04 15:30:14
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Preparation of Ultra-low Temperature Sintering Ceramics with Ultralow Dielectric Loss in Na <sub/>2</sub> O-WO <sub/>3</sub> Binary System
摘要： A series of new microwave dielectric ceramics with ultralow dielectric loss in Na2O-WO3 binary system were prepared by the modified solid-state reaction method at ultra-low sintering temperatures. Three stable phases, namely Na2WO4, Na2W2O7 and Na2W4O13, were formed in the system. Their stability in the air, phase composition, compatibility with metal electrodes, microstructures and microwave dielectric properties were investigated. In this binary system, the cubic structure Na2WO4 ceramic sintered at 565?C exhibited the best microwave dielectric properties with a permittivity of 5.6, a Q × f value of 124 200 GHz and a temperature coefficient of -63 ppm/?C at a frequency of 13.1 GHz. The Na2WO4 ceramic is chemically compatible with Ag and Al electrodes. Besides, the Na2WO4 ceramic has favorable stability in the air. Due to the excellent dielectric properties and favorable stability in the air, the Na2WO4 ceramic is a great candidate for LTCC devices.
关键词： Ultra-low dielectric loss,Microwave dielectric ceramics,Ultra-low firing
更新于2025-09-04 15:30:14
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Structure, dielectric properties of low-temperature-sintering BaTiO <sub/>3</sub> -based glass–ceramics for energy storage
摘要： The 0.85BaTiO3–0.15Bi(Mg2/3Nb1/3)O3 (BTBMN) ceramics with low-melting-temperature B2O3–Na2B4O7–Na2SiO3 (BNN) glass addition were prepared by the solid state method. The composition of the glass–ceramics was BTBMN–x wt.% BNN (x = 0, 1, 3, 5, 7, 9, 12, 15; abbreviated as BG). The sintering characteristics, phase structure, microstructure, dielectric properties and energy storage properties were systematically investigated. The sintering temperature of BTBMN ceramics was greatly reduced by the addition of BNN glass. The second-phase BaTi(BO3)2 was observed in the BG system until the glass content reached 15 wt.%. The addition of BNN glass significantly reduces the grain size of BTBMN ceramics. With the increase of BNN glass content, dielectric constant of BG glass–ceramics at 1 kHz gradually decreased, the maximum dielectric constant (εm) of BG glass–ceramics gradually decreased, while the temperature corresponding to the maximum dielectric constant (Tm) increased, the ferroelectric relaxation behavior decreased and the temperature stability of the dielectric constant gradually improved. As the BNN glass content increased, the breakdown electric field strength (BDS) of BG glass–ceramics increased first and then decreased, and the polarization values reduced gradually, while the trend of energy storage performance is similar to BDS. When the BNN glass content was 3 wt.%, the energy storage properties of the BG glass–ceramics were optimal, and a recoverable energy storage density (Wrec) of 1.26 J/cm3 and an energy storage efficiency (η) of 80.9% were obtained at the electric field strength of 220 kV/cm. The results showed that BG glass–ceramics were promising for energy storage capacitors.
关键词： Lead-free,glass–ceramics,relaxation,energy storage properties,BaTiO3
更新于2025-09-04 15:30:14
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Recent development of A2B2O7 system transparent ceramics
摘要： A2B2O7 system compounds, which usually present three phase structures mainly based on the ionic radius ratios of rA and rB (rA/rB), have been studied for potential applications in many fields, such as thermal barrier coatings, luminescence powders, fast-ion conductors, photocatalysts, and matrices for immobilization of highly active radionuclides. Since 2005, La2Hf2O7 was fabricated into transparent ceramics and much more attentions were paid on A2B2O7 transparent ceramics for new applications. In this review, the development of A2B2O7 system transparent ceramics was described. The structure characteristics, powder synthesis method, and sintering techniques of the final A2B2O7 transparent ceramics were summarized. After that, the mostly reported A2Hf2O7, A2Zr2O7, and A2Ti2O7 system transparent ceramics were systematically introduced. The potential application fields and future development trends were also discussed, focusing on scintillators, optical elements, and other luminescent materials.
关键词： A2B2O7 system transparent ceramics,potential applications,sintering,powder synthesis
更新于2025-09-04 15:30:14
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Red-emission properties and crystallization behavior in Eu2O3-TeO2 glasses
摘要： Transparent glass of xEu2O3-(100-x)TeO2 binary system is obtained by using the melt-quenching method and especially studied for x = 5 in xEu2O3-(100-x)TeO2 composition. Optical properties such as transmission, excitation, and emission spectra of Eu2O3-TeO2 glass-ceramics are studied and carefully compared for the samples heated at di?erent temperatures. The one step heat-treatment a?ects the crystallinities as well as phase formation and yields cubic [Eu2Te6O15], orthorhombic [TeO2], and tetragonal [TeO2] phases depending on the heat treating temperature. Glass-ceramics of Eu3+-doped tetragonal [TeO2] shows stronger emission intensity at wavelength of 613 nm with an excitation wavelength of 394 nm compared with that from cubic [Eu2Te6O15] or Eu3+-doped orthorhombic [TeO2]. Enhancement of emission intensity in Eu3+-doped tetragonal [TeO2] is related to the local environment of Eu3+ ions substituted in tetragonal TeO2 lattice.
关键词： Tellurite glasses,Glass-ceramics,Optical property,Eu2Te6O15 crystal
更新于2025-09-04 15:30:14
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Dielectric Properties of NaCu <sub/>3</sub> Ti <sub/>3</sub> Nb <sub/>1–x</sub> Sb <sub/>x</sub> O <sub/>12</sub> Ceramics
摘要： In order to investigate the influence of Sb doping on the dielectric properties of NaCu3Ti3NbO12 ceramics, a series of NaCu3Ti3Nb1–xSbxO12 ceramics were prepared by conventional solid-state reaction technique. Their crystalline structure, microstructure, dielectric properties and complex impedance were systematically investigated. All these ceramics show giant permittivity phenomenon, and their low-frequency dielectric loss decrease significantly but permittivity remains large with increased Sb doping. Impedance spectroscopic analysis reveals that NaCu3Ti3Nb1–xSbxO12 ceramics are composed of insulating grain boundaries and semiconducting grains, and their resistance of grain boundary increases with increased Sb doping. According to internal barrier layer capacitance effect, the decrease of low-frequency dielectric loss in NaCu3Ti3Nb1–xSbxO12 ceramics with increased Sb doping should be caused by the increase of grain boundary resistance.
关键词： Internal barrier layer capacitance effect,NaCu3Ti3Nb1–xSbxO12 ceramics,Grain boundary resistance,Low-frequency dielectric loss
更新于2025-09-04 15:30:14
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Análise da expans?o térmica volumétrica e das características estruturais de solu??es sólidas de (Pb, Ca)TiO3 entre 150 e 570 K
摘要： Ceramic samples of lead modified calcium titanate (Pb1-xCaxTiO3) with calcium concentration between 0.24≤x≤0.55 were prepared and analyzed in order to determine the structural origin of the negative thermal expansion observed in this ferroelectric system. The Rietveld structural refinement method was used to assess the thermal evolution of the structural parameters using powder X-ray diffraction data collected between 150 and 570 K. Since the Pb1-xCaxTiO3 phase diagram and space groups are still unknown for the temperature range investigated, the structural analyses were based on adjustments of the refinement protocol. The results revealed the existence of a correlation between symmetry transitions and anomalies in the thermal expansion of the unit cell, being such transitions not necessarily of the ferroelectric-paraelectric nature.
关键词： Rietveld refinement method,symmetry transitions,structural analyses,unit cell thermal expansion,ferroelectric ceramics
更新于2025-09-04 15:30:14
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Effect of doping Gd2O3 on dielectric and piezoelectric properties of BaZr0.1Ti0.9O3 ceramics by sol–gel method
摘要： The effects of sintering temperature and doping amount of gadolinium ions on the microstructures and electrical properties of sol gel derived Ba (Zr0.1Ti0.9) O3 + xGd ceramics were investigated in this manuscript. XRD analysis showed that the main crystalline phase of BZT-xGd ceramic samples exhibit a perovskite structure without significantly change. The sample sintered at 1350 °C and doped with gadolinium ions of 0.5 mol% has uniform grain size and compact morphology. And the sample(1350 °C—0.5 mol%) also has a high piezoelectric charge coefficient of 131.33 pC/N, large plane electromechanical coupling coefficient of 0.22, high dielectric constant of 10504, and small dielectric loss of 0.01. The correlation of dielectric and piezoelectric properties of BZT-xGd ceramics with doping amount of Gd3+ ion has been explained by the lattice theory.
关键词： BZT-xGd ceramics,dielectric properties,sol–gel method,gadolinium doping,piezoelectric properties
更新于2025-09-04 15:30:14
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Synthesis, structural and optical‐vibration properties of Ba <sub/>3</sub> Sc <sub/>4</sub> O <sub/>9</sub> and Sr <sub/>3</sub> Sc <sub/>4</sub> O <sub/>9</sub> ceramics
摘要： Ba3Sc4O9 and Sr3Sc4O9 ceramics were synthesized by conventional solid‐state reactions at 1200°C, being further sintered at 1300°C in order to produce ceramic bodies suitable for exploring their structural and optical vibration properties. Optimized experimental conditions were employed to unveil the complex vibrational spectra of these ceramics by polarized Raman scattering. A reliable and comprehensive set of phonon features was obtained from these experiments: The 30 theoretically expected optically active lattice modes for each material were in fact observed, from which 15 could be assigned as totally symmetric A‐polar modes and 15 attributed as degenerate (and asymmetric) E‐polar ones. Differences between experimental data of Ba‐containing and Sr‐containing samples are discussed in terms of their ionic radii and molar masses. The knowledge of the optical phonon features reported here can help to understand the exceptional luminescence properties of Ba3Sc4O9 and Sr3Sc4O9 rhombohedral phases when doped with trivalent ions, as recently reported by the literature.
关键词： luminescence,ceramics,phosphors,Ba3Sc4O9 and Sr3Sc4O9,polarization‐resolved Raman spectroscopy
更新于2025-09-04 15:30:14