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Structural and dielectric properties of sol–gel derived Ba<sub>1–<i>x</i></sub>Sr<sub><i>x</i></sub>TiO<sub>3</sub> (0 ≤ <i>x</i> ≤ 0.5) ceramics for energy storage applications
摘要： Barium strontium titanate (Ba1–xSrxTiO3, BSTO: x = 0, 0.3 and 0.5) ceramics were prepared by sintering sol–gel derived BSTO powders at 1350 °C for 2 h. Average grain size of BSTO ceramics decreased from 15 to 2 μm with increasing Sr molar fraction. X-ray structural analysis revealed that BSTO ceramics exhibited tetragonal structure (x = 0 and 0.3) and transformed into cubic structure at high Sr molar fraction (x = 0.5) at room temperature. Dielectric constant of the BSTO ceramics was measured between ?60 and 180 °C and frequency range of 1–100 kHz. Temperature transition from ferroelectric to paraelectric phase (Curie temperature: TC) decreased linearly from 125 to ?30 °C as Sr molar fraction increased. The dielectric constant exhibited frequency-independent behavior in the frequency range investigated. A diffuse dielectric constant peak was evident for BSTO with Sr molar fraction of 0.5 due to the effect of fine-grained size. Polarization–electric field (P–E) at room temperature presented a well-defined hysteresis loop for BSTO (x = 0 and 0.3), indicating their ferroelectric characteristics. At a high Sr molar fraction of 0.5, the P–E loop became a linear relation, indicating a paraelectric phase. Energy storage density of BSTO with x = 0 was about 0.2 J/cm3; however, energy storage efficiency was less than 50%. After doping with Sr molar fraction of 0.5, energy storage density decreased to 0.1 J/cm3 but its energy storage efficiency significantly improved to 90%.
关键词： sol-gel method,dielectric,energy storage capacitors,barium strontium titanate
更新于2025-09-23 15:21:01
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Effect of the occupation of Ba and Ti sites on the structural, optical and dielectric properties of Sm-doped BaTiO3 ceramics
摘要： Sm-doped BaTiO3 powders have been synthesized with the help of the sol gel process. X-ray diffraction (XRD) patterns of the obtained powders, heat treated at a relatively low temperature (750 °C/3 h), revealed their crystallization in the pure perovskite structure without the presence of secondary phases. The occupation of the Ba and Ti sites by Sm in the BaTiO3 lattice and the evolution of the crystalline parameters as functions of the dopant content have been discussed based on XRD and Raman results. Dielectric measurements performed on the samples revealed a strong increasing diffuse character of the ferro-to-paraelectric phase transition with increasing Sm content. Moreover, the behavior of the permittivity as a function of frequency indicates that the samples are approaching their resonance frequency. The study of the conductivity showed the existence of a weak positive temperature coefficient of resistivity (PTCR) effect.
关键词： Sm-doped BaTiO3,dielectric properties,PTCR effect,perovskite structure,sol gel process
更新于2025-09-23 15:21:01
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Role of co-doping on structural, optical and magnetic properties of nano-crystalline ZnO thin films
摘要： This paper refers to investigation of structure, surface morphology, optical parameters and magnetic characteristics of the prepared ZnO thin films when Co concentration varies from 1 to 5 at wt %. X-ray diffraction study revealed that deposited films were poly-crystalline with hexagonal wurtzite structure. The band gap energy was calculated by using the envelope method. It’s value was decreased from 3.334 to 3.22 eV with increasing Co concentration up to 4 at wt % and then increased to 3.335 eV for 5 at wt% Co. The magnetic study indicated a ferromagnetic trend for all thin films. An oxygen vacancies–related F-center is a possible physical mechanism for generation of ferromagnetism. Scanning Electron Microscopy exhibited rough and porous morphology.
关键词： sol-gel,Thin films,ZnO,Ferromagnetism,doping
更新于2025-09-23 15:21:01
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Contents: (Adv. Funct. Mater. 44/2018)
摘要： Silica nanofibrous membranes produced by direct electrospinning of a sol-gel solution without a sacrificing polymer allow high-end separation and purification due to a high thermal and chemical resistance. The water repellent or absorbing nature can be tuned by applying a humidity or thermal treatment. It is showcased that fast gravity driven membrane separation of heterogeneous azeotropes can be achieved.
关键词： thermal resistance,chemical resistance,sol-gel,electrospinning,azeotrope separation,silica nanofibrous membranes
更新于2025-09-23 15:21:01
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Microwave Sol-Gel Derived PbY2(MoO4)4:Er3+/Yb3+ Double Molybdate and Their Up-Converted Optical Properties
摘要： PbY2-x(MoO4)4:Er3+/Yb3+ double molybdate phosphors with the correct doped concentrations of Er3+ and Yb3+ (x = Er3+ + Yb3+, Er3+ = 0, 0.05, 0.1, 0.2 and Yb3+= 0, 0.2, 0.45) were precisely prepared using the sol-gel method assisted by the microwave technique; their up-converted optical properties were studied. The particles showed well-crystallized morphology after heat-treated at 900 °C for 16 h. They had a homogeneous and fine morphology with grain sizes of 2-5 μm. After excitation at 980 nm, the PbY1.7(MoO4)4:Er0.1/Yb0.2 and PbY1.5(MoO4)4:Er0.05/Yb0.45 double molybdates provided a strong up-converted emission band of 525 nm, a weak up-converted emission band of 550 nm in the green region and a very weak up-converted emission band of 655 nm in the red region. The spectroscopic spectra of Raman for the doped molybdates showed the presence of strong peaks at higher and lower frequencies. It was induced by highly modulated structures of PbY2-x(MoO4)4 by the incorporation of the Er3+ and Yb3+ ions into the crystal lattice. These results were attributed to the unit cell shrinkage as well as the anion deficient of the MoO4-x group.
关键词： PbY2-x(MoO4)4:Er3+/Yb3+,Sol-gel,Up-converted photoluminescence,Raman spectroscopy,Microwave
更新于2025-09-23 15:21:01
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XPS and thermal studies of silver doped SiO2 matrices for plasmonic applications
摘要： Silver nanocrystals doped SiO2 matrices were synthesized through sol–gel route using acid catalyst. The prepared silica matrices with different concentrations of silver were annealed at different temperatures and characterized using, XRD, FTIR, Absorption spectroscopy, XPS, thermogravimetric and differential thermal analysis. The XRD data con?rm the amorphous nature of silica and crystalline nature of silver nanocrystals. Using the Fourier-transform infrared red spectrum the formation of silica glass was con-?rmed. The characteristic Surface Plasmon Resonance of silver nanoparticles obtained around 400 nm from the absorption spectrum. The observed blue shift and skewness in SPR with increasing silver con-centrations were studied. The 3d doublet state of silver at a binding energy of 368.4 eV with the splitting of 6 eV obtained in XPS con?rm the state Ag0 along with the presence of a minor quantity of silver (II) oxide. The thermal stability and nature were analyzed using TGA-DTG and DTA and showed good thermal stability from 400 (cid:1)C to higher temperatures.
关键词： Sol-gel,Surface plasmon resonance,Thermal analysis,XPS,Silver nanocrystals
更新于2025-09-23 15:19:57
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MgxZn1a??xO Prepared by the Sola??Gel Method and Its Application for Ultraviolet Photodetectors
摘要： MgxZn1(cid:2)xO (x = 0.05, 0.10, 0.15, and 0.20) ?lms prepared on quartz substrates by the sol–gel method were characterized and studied. According to scanning electron microscopy and x-ray diffraction data, the MgxZn1(cid:2)xO ?lms exhibited a particle-stacking morphology and a hexagonal wurtzite crystal structure. An increase in Mg content led to an obvious increase in particle size. However, a weakening of the hexagonal wurtzite structure was observed and indicated the transition of the MgxZn1(cid:2)xO crystal structure, which was also con?rmed by the Raman spectra results. An increase in bandgap energy from 3.38 eV to 3.55 eV with increased Mg content was determined from the transmittance spectra. Ultraviolet photodetectors based on MgxZn1(cid:2)xO with interdigital electrodes were then fabricated. Dark current as low as 10 pA (corresponding to 5 nA/cm2) under bias of 10 V was achieved. A blueshift of the peak wavelength and cutoff wavelength was observed with increasing Mg content. Noise equivalent power as low as 2 9 10(cid:2)15 W was achieved, detectivity was found to be about 1.2 9 1011 cm Hz1/2/W, and quantum ef?ciency was nearly 100%, which was related to the photoconductive gain.
关键词： sol–gel,bandgap,MgxZn1(cid:2)xO,ultraviolet photodetectors
更新于2025-09-23 15:19:57
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Thin silica-based microsheets with controlled geometry
摘要： A high demand for materials with defined geometry and size is required in a wide range of fields. Inorganic compounds, especially silica-based, arise as a cheap source and chemically flexible for the purpose. Silica display unique properties, like easy functionalization and good optical to manipulate. In this work, we developed a method to create thin silica microsheets with defined size and high-fidelity shape using superhydrophobic-hydrophilic microarrays. These microstructures were produced through sol-gel process using biomimetic superhydrophobic surfaces decorated with wettable spots. The results confirm the manufacture of porous silica microstructures with defined design (squares and circles) and thickness around 7 μm. The methodology applied in this work enables the high throughput fabrication of shaped silica materials in a single step, unlocking an extensive number of applications in areas that require miniaturization, like microelectronics or in fields like sensing and biomedicine.
关键词： Silica microsheets,High-fidelity shape,Inorganic materials,High throughput,Sol-gel process
更新于2025-09-23 15:19:57
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Enhancement of power conversion efficiency of Al/ZnO/p-Si/Al heterojunction solar cell by modifying morphology of ZnO nanostructure
摘要： This paper proposes a cost-effective sol–gel method for synthesis of ZnO nanostructure to make Al/ZnO/p-Si/Al heterojunction solar cell. Here, crystalline ZnO nanostructure was grown on p-silicon and annealed at 300 °C, 400 °C and 500 °C for application in heterojunction solar cell. The optimum temperature for obtaining uniform crystalline nanostructure was 500 °C, as confirmed from XRD and SEM imaging. As investigated by UV–Vis spectroscopy, the ZnO nanostructure layer exhibited high transmittance in the visible spectrum and has a direct band gap of 3.26–3.28 eV. The power conversion efficiency of Al/ZnO/p-Si/Al solar cell is enhanced from 1.06 to 2.22% due to increase in surface area of ZnO by formation of crystalline nanostructure due to increase of annealing temperature. The optimum value of short-circuit current (Isc) and open-circuit voltage (Voc) was measured using current–voltage (I–V) under AM 1.5 illuminations and found to be 9.97 mA and 460 mV, respectively.
关键词： Power conversion efficiency,Sol–gel method,Annealing temperature,Heterojunction solar cell,ZnO nanostructure
更新于2025-09-23 15:19:57
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A sola??gel synthesis to prepare size and shape-controlled mesoporous nanostructures of binary (IIa??VI) metal oxides
摘要： A base-catalyzed sol–gel approach combined with a solvent-driven self-assembly process at low temperature is augmented to make manganese oxide (Mn3O4), copper oxide (CuO), and magnesium hydroxide (Mg(OH)2) nanostructures with size- and shape-controlled morphologies. Nanostructures of Mn3O4 with either hexagonal, irregular particle, or ribbon shape morphologies with an average diameter ranged from 100 to 200 nm have been prepared in four di?erent solvent types. In all morphologies of Mn3O4, the experimental XRD patterns have indexed the nanocrystal unit cell structure to triclinic. The hexagonal nanoparticles of Mn3O4 exhibit high mesoporocity with a BET surface area of 91.68 m2 g?1 and BJH desorption average pore diameter of ～28 nm. In the preparation of CuO nanostructures, highly nanoporous thin sheets have been produced in water and water/toluene solvent systems. The simulated XRD pattern matches the experimental XRD patterns of CuO nanostructures and indexes the nanocrystal unit cell structure to monoclinic. With the smallest desorption total pore volume of 0.09 cm3 g?1, CuO nanosheets have yielded the lowest BET surface area of 18.31 m2 g?1 and a BHJ desorption average pore diameter of ～16 nm. The sol of magnesium hydroxide nanocrystals produces highly nanoporous hexagonal nanoplates in water and water/toluene solvent systems. The wide angle powder XRD patterns show well-de?ned Bragg's peaks, indexing to a hexagonal unit cell structure. The hexagonal plates show a signi?cantly high BET surface area (72.31 m2 g?1), which is slightly lower than the surface area of Mn3O4 hexagonal nanoparticles. The non-template driven sol–gel synthesis process demonstrated herein provides a facile method to prepare highly mesoporous and nanoporous nanostructures of binary (II–VI) metal oxides and their hydroxide derivatives, enabling potential nanostructure platforms with high activities and selectivities for catalysis applications.
关键词： catalysis applications,size and shape-controlled morphologies,mesoporous nanostructures,binary (II–VI) metal oxides,sol–gel synthesis
更新于2025-09-23 15:19:57