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Controlled hydrothermal synthesis of different sizes of BaTiO<sub>3</sub> nano-particles for microwave absorption
摘要： Different sizes of barium titanate (BaTiO3) nano-particles were synthesized from precursor H2Ti3O7 nanotubes through facile hydrothermal synthesis by using EtOH/H2O as mixing solvent. Field-emission scanning electron microscopy (FESEM) was mainly used to investigate the effects of solution alkalinity, polarity, and hydrothermal temperature on the size and morphology evolution of BaTiO3 nanoparticles. The results indicate that the presence of strong alkalinity improved the size evenness of BaTiO3 nanoparticles possibly because of the re-dissolution and re-precipitation of TiO3 2- ions. As for the reason, the addition of EtOH could lower the polarity of hydrothermal medium and make the medium reach the supersaturation more easily, thus limiting the size growth of BaTiO3 particles. In addition, the presence of EtOH led to easier formation of BaTiO3 nanoparticles even at mild hydrothermal temperature, but the particle size was limited even though the temperature was much increased. This is possibly due to lowered interfacial activity in the presence of EtOH. By adjusting solution alkalinity, EtOH/H2O volume ratios, and hydrothermal temperature, BaTiO3 nanoparticles with the average sizes of approximately 21, 53, 104, 284, and 512 nm, were obtained, and more different and controlled nano-sizes can be expected by further hydrothermal adjustment. In the end, microwave absorption evaluation indicated that the decreased size of the BaTiO3 particles enhanced the reflection loss. One possible reason is that the decreased nano-size led to the increased specific surface area of the BaTiO3 nanoparticles.
关键词： Hydrothermal synthesis,Barium titanate,Polarity,Temperature,Microwave absorption,Adjustable nano-size
更新于2025-09-16 10:30:52
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Ultra-Low Power Tuning in Hybrid Barium Titanate-Silicon Nitride Electro-Optic Devices on Silicon
摘要： As the optical analogue to integrated electronics, integrated photonics has already found widespread use in data centers in the form of optical interconnects. As global network traffic continues its rapid expansion, the power consumption of such circuits becomes a critical consideration. Electrically-tunable devices in photonic integrated circuits contribute significantly to the total power budget as they traditionally rely on inherently power-consuming phenomena such as the plasma dispersion effect or the thermo-optic effect for operation. Here, we demonstrate ultra-low power refractive index tuning in a hybrid barium titanate (BTO)-silicon nitride (SiN) platform integrated on silicon. We achieve tuning by exploiting the large electric field-driven Pockels effect in ferroelectric BTO thin films of sub 100 nm thickness. The extrapolated power consumption for tuning a free spectral range (FSR) in racetrack resonator devices is only 106 nW/FSR, several orders of magnitude less than many previous reports. We demonstrate the technological potential of our hybrid BTO-SiN technology by compensating thermally-induced refractive index variations over a temperature range of 20 °C and by using our platform to fabricate tunable multi-resonator optical filters. Our hybrid BTO-SiN technology significantly advances the field of ultra-low power integrated photonic devices and allows for the realization of next-generation efficient photonic circuits for use in a variety of fields, including communications, sensing, and computing.
关键词： ferroelectric,Pockels effect,silicon nitride,electro-optic,barium titanate,integrated photonics,optical tuning
更新于2025-09-16 10:30:52
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Dielectric and thermal behavior of 0.75BiFeO3-0.25BaTiO3 filled ethylene vinyl acetate Composites
摘要： Bismuth ferrite-Barium Titanate (BFO-BT) filled ethylene-vinyl acetate copolymer (EVA) composites have been processed by solution casting technique followed by compression molding. The effects of BFO-BT on structural, thermal and dielectric behaviour of the composites have been investigated using X-ray diffraction, field emission scanning electron microscopy, thermal analysis (DSC, TGA) and impedance analyser. As analysed by XRD and DSC analyses, with increase in BFO-BT content the crystallinity of EVA matrix decreases. BFO-BT has great effect on higher thermal stability of the composites. EVA/ BFO-BT composites exhibit significantly enhanced relative dielectric permittivity (εr =182) near the percolation limit of about 30 phr BFO-BT loading at 25° C and 1kHz frequency. With 30 phr BFO-BT loading, the dielectric loss of the composite shows only an approximately 2-fold increase i.e., from 0.04 to 0.091. The capacitance and resistance of grains is found from the exploratory Nyquist plots with the assistance of an electrical circuit. A cautious examination of the experimental complex impedance plots and model fitted plots is contemplated which fulfilled the precision of the information tentatively. With enhanced dielectric properties and thermal stability, the BFO-BT filled EVA composite system can be used for solar cells and energy saving devices.
关键词： Composites,Nyquist plots,Dielectric,Conductivity,Ethylene Vinyl Acetate,Bismuth Ferrite-Barium Titanate
更新于2025-09-12 10:27:22
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Enhancing the charge extraction and stability of perovskite solar cells using strontium titanate (SrTiO3) electron transport layer
摘要： Charge transport layers strongly influence the performance of perovskite solar cells (PSCs). To date, compact layers and mesoporous scaffolds of titanium dioxide have emerged as good electron transport layers (ETL), enabling record power conversion efficiencies (PCE). However, these ETLs require sintering above 400 °C, which excludes them from low-temperature applications such as flexible devices and silicon-heterojunction tandems. Furthermore, instability of TiO2 under prolonged exposure to sun light appears to be a critical issue. Here, we present the promising characteristics of low-temperature processed strontium titanate (STO) as an ETL to realize PSCs with 19% PCE. STO is a wide bandgap transparent inorganic perovskite. Compared to other low-temperature processed interlayers, STO reduces the parasitic absorption in the ultraviolet and visible range, improves the electron transport and greatly increases the stability of the devices, retaining ~80% of their initial efficiency after 1000 hours of constant white light illumination.
关键词： perovskite solar cells,stability,low-temperature processing,strontium titanate,electron transport layer
更新于2025-09-12 10:27:22
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Ferroelectric PZT thin films for photovoltaic application
摘要： The ferroelectric photovoltaic response characteristics of Lead Zirconate Titanate (PZT) thin film in metal-ferroelectric-metal (MFM) configuration is studied under 33 mode upon exposure to UV radiations. PZT thin films of 180 nm are prepared on inter-digital electrodes patterned silicon substrate (with silicon dioxide as insulating layer) using chemical solution deposition (CSD) technique followed by rapid thermal annealing. PZT thin films are found to be in single phase and possess high electrical polarization (50μC/cm2). Significant increase in photocurrent and large value of open circuit voltage (1.0 V) is observed for the prepared ferroelectric photovoltaic film under UV illumination.
关键词： Lead zirconium titanate,Chemical deposition,Polarization,Ferroelectric,Photovoltaics
更新于2025-09-12 10:27:22
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Defect characterization of slow-cooled and quenched samples of calcium-copper-titanate through positron annihilation spectroscopy
摘要： Positron annihilation lifetime and Doppler-broadened gamma-ray spectra have been analyzed for slow-cooled and thermally quenched polycrystalline samples of calcium-copper-titanate. Two positron lifetimes revealing the characteristic defects in the respective samples were carefully analyzed to compare and contrast the significance of their origin and implication. A third component arising from positronium formation at the powdered particle surfaces has been considered in the analysis although its significance is lost in its very small intensity ((cid:1) 1.1–1.2%). In the quenched sample, the defect-specific long positron lifetime (s2) is found to larger and the mean lifetime smaller while its intensity I2 is found drastically smaller and the concentration of defects less by an order of magnitude as compared to the slow-cooled sample. The observed changes in electrical parameters of slow-cooled and quenched samples were found to have correlations with the positron annihilation lifetime and Doppler-broadened lineshape parameters.
关键词： defects,vacancies,positron annihilation,Calcium-copper-titanate,quenching
更新于2025-09-12 10:27:22
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A study on electro-optical properties of polymer dispersed liquid crystal films doped with barium titanate nanoparticles prepared by nucleophile-initiated thiol-ene click reaction
摘要： Polymer-dispersed liquid crystal (PDLC) films doped with barium titanate (BTO) nanoparticles were prepared by nucleophile-initiated thiol-ene click reaction. The effects of BTO content and reaction temperature on the electro-optical properties of PDLC were explored. It is found that the size of liquid crystal droplets is bigger when the amount of BTO increases. As the BTO content increases, the transmittance first rises and then falls, while the voltage that drives the liquid crystal orientation first drops and then rises. The electro-optical properties of PDLC doped with BTO show a similar changing trend with the change of reaction temperature. However, when the reaction temperature becomes higher, the influence of BTO on the electro-optical properties of PDLC becomes greater. Doping BTO helps to obtain PDLC films with good electro-optical properties.
关键词： reaction temperature,PDLC,barium titanate nanoparticles,electro-optical properties
更新于2025-09-12 10:27:22
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Ferroelectric barium titanate derivatives containing Mo and Mg for transparent photovoltaic applications
摘要： Using first-principles methods, we investigate the electronic properties of the [Ba(Mo1/2,Mg1/2)O3]x-[BaTiO3]1?x solid solution derived from barium titanate as a potential candidate to be used in photovoltaic devices. Focusing on the bandgap and its origin, we study the effect of different possible Mo and Mg contents, arrangements, and phases of [Ba(Mo1/2,Mg1/2)O3]x-[BaTiO3]1?x. We find that [Ba(Mo1/2,Mg1/2)O3]0.25-[BaTiO3]0.75 is a viable candidate for use in transparent photovoltaics due to its energy bandgap of 2.6 eV in the rhombohedral phase. In all cases, [Ba(Mo1/2,Mg1/2)O3]x-[BaTiO3]1?x materials exhibit spontaneous polarization that allows the exploitation of the bulk photovoltaic effect and in principle may allow high power conversion efficiency exceeding the Shockley-Queisser limit for these materials.
关键词： ferroelectric,photovoltaic,transparent,bandgap,barium titanate
更新于2025-09-11 14:15:04
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Island growth mode in pulsed laser deposited ferroelectric BaTiO <sub/>3</sub> thin films: The role of oxygen pressure during deposition
摘要： Pulsed laser deposition is widely used to grow BaTiO3 thin films. We investigated the influence of oxygen pressure during growth on the topography, microstructure, and roughness of ferroelectric epitaxial BaTiO3 thin films. It also presented an analysis of the epitaxial growth mode and defects throughout the film thickness using aberration-corrected transmission electron microscopy. Although ferroelastic (twin boundary) domain walls are absent, several misfit dislocations were observed and might be the primary cause of the observed island growth mode.
关键词： barium titanate,Ferroelectric thin film,epitaxial thin film,misfit strain,crystalline defects
更新于2025-09-11 14:15:04
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Influence of Semiconductor Morphology on Photocatalytic Activity of Plasmonic Photocatalysts: Titanate Nanowires and Octahedral Anatase Nanoparticles
摘要： Octahedral anatase particles (OAP) with eight exposed and thermodynamically most stable (101) facets were prepared by an ultrasonication-hydrothermal (US-HT) reaction from potassium titanate nanowires (TNW). The precursor (TNW) and the product (OAP) of US-HT reaction were modi?ed with nanoparticles of noble metals (Au, Ag or Pt) by photodeposition. Samples were characterized by X-ray di?raction (XRD), X-ray photoelectron spectroscopy (XPS), di?use re?ectance spectroscopy (DRS), scanning transmission electron microscopy (STEM) and time-resolved microwave conductivity (TRMC). The photocatalytic activity was investigated in three reaction systems, i.e., anaerobic dehydrogenation of methanol and oxidative decomposition of acetic acid under UV/vis irradiation, and oxidation of 2-propanol under vis irradiation. It was found that hydrogen liberation correlated with work function of metals, and thus the most active were platinum-modi?ed samples. Photocatalytic activities of bare and modi?ed OAP samples were much higher than those of TNW samples, probably due to anatase presence, higher crystallinity and electron mobility in faceted NPs. Interestingly, noble metals showed di?erent in?uence on the activity depending on the semiconductor support, i.e., gold-modi?ed TNW and platinum-modi?ed OAP exhibited the highest activity for acetic acid decomposition, whereas silver- and gold-modi?ed samples were the most active under vis irradiation, respectively. It is proposed that the form of noble metal (metallic vs. oxidized) as well as the morphology (well-organized vs. uncontrolled) have a critical e?ect on the overall photocatalytic performance. TRMC analysis con?rmed that fast electron transfer to noble metal is a key factor for UV activity. It is proposed that the e?ciency of plasmonic photocatalysis (under vis irradiation) depends on the oxidation form of metal (zero-valent preferable), photoabsorption properties (broad localized surface plasmon resonance (LSPR)), kind of metal (silver) and counteraction of “hot” electrons back transfer to noble metal NPs (by controlled morphology and high crystallinity).
关键词： silver,platinum,gold,photocatalyst morphology,faceted titania,morphology-governed activity,plasmonic photocatalysis,octahedral particle,titanate nanowire,noble metal
更新于2025-09-11 14:15:04