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Effect of strain on the modifications in electronic structure and resistive switching in Ca-doped BiFeO <sub/>3</sub> films
摘要： Strain-induced modifications in the structure, electronic structure, electrical, and ferroelectric properties of the Bi0.90Ca0.10FeO3 (BCFO)/Nb-doped SrTiO3 (100) films have been systematically studied in light of variation in film thickness. X-ray diffraction and ?-scan measurements confirm the single phase, (100) oriented epitaxial growth of all films. Room temperature absorption spectra show the presence of asymmetric broad peak around ～2.5 eV, which is indicative of the presence of defect states inside the bandgap and is attributed to the oxygen vacancies. Improvement in the bipolar resistive switching behavior with a decrement in oxygen vacancies and improvement in ferroelectric properties with increasing film thickness suggest the crucial role of oxygen vacancies and strain in modifying the electrical properties of the BCFO films. Improvement in the ferroelectric behavior is attributed to the increment in the Fe 3d-O 2p hybridization, localization of Fe 3deg/Bi 6s-O 2p orbitals, and reduction in the oxygen vacancies with an increase in the film thickness. Observed stable retention and large ON/OFF switching ratio in BCFO films make them a promising candidate for application in the non-volatile memory device.
关键词： Ca-doped BiFeO3 films,resistive switching,ferroelectric properties,strain,electronic structure
更新于2025-09-04 15:30:14
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Dielectric and Ferroelectric Response of Multiphase Bi-Fe-O Ceramics
摘要： The structural, dielectric, and ferroelectric characterization of multiphase Bi-Fe-O prepared with an excess of Bi up to 20% is reported. It is found that the dominant phase in all samples is the BiFeO3 perovskite in addition to an increasing amount of the Bi-rich sillenite phases (Bi12.5Fe0.5O19.48/Bi25FeO39) with the Bi excess content. At room temperature, the multiphase Bi-Fe-O results in advanced electrical properties, with higher dielectric constant (161 at 1 MHz) and low losses (tanδ ? 0.032 at 1 MHz). The ferroelectric character of multiphase ceramics is confirmed by PUND measurements, which shows increased polarization values and coercive field with respect to the single phase ceramics.
关键词： impurity phases,bismuth ferrite,PUND ferroelectric characterization,dielectric characterization,multiferroics
更新于2025-09-04 15:30:14
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Influence of uniaxial pressure on dielectric properties of (1- <i>x</i> )Na <sub/>0.5</sub> Bi <sub/>0.5</sub> TiO <sub/>3–</sub><i>x</i> SrTiO <sub/>3</sub> for <i>x</i> = 0.01, 0.04, and 0.1 ceramics
摘要： The conventional solid-state sintering was applied to synthesized (1-x)Na0.5Bi0.5TiO3–xSrTiO3 (x = 0.01, 0.04, and 0.1) ceramics. Dielectric measurements of these ceramics were taken in the temperature range from 20 to 600 °C, in the frequency range from 1 kHz to 2 MHz and under uniaxial pressure ranging from 10 to 1100 bar. The study of the dielectric behaviour showed that the influence of uniaxial pressure on the investigated properties was considerable. The peaks ?m gradually decreased and shifted towards lower temperatures with an increase of uniaxial pressure for all samples. The first effect developed with an increase of the strontium ion concentration. Experimental results revealed most interesting properties of the material in the context of its potential applications.
关键词： perovskite,uniaxial pressure,ferroelectric materials,dielectric spectroscopy
更新于2025-09-04 15:30:14
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Structure evolution and ferroelectric properties in stoichiometric Bi0.5+xNa0.5?xTi1?0.5xO3
摘要： The influence of B-site deficiency on the stability of electrically induced long-range ferroelectric order of Bi0.5+xNa0.5-xTi1-0.5xO3 (BNT-xVTi) (''h'' denotes vacancies) ceramics is studied. The depolarization and ferroelectric to relaxor transition are identified as separate and discrete processes in BNT-based materials. For BNT-0.02VTi, the resonance and anti-resonance peaks on dielectric permittivity-frequency curves indicate dominating ferroelectric phase at room temperature. The depolarization temperature, determined by thermally stimulated depolarization current, is * 65 °C. However, the ferroelectric to relaxor transition temperature is absent, as no distinct frequency-independent anomalies for the dielectric permittivity exist. This depolarization process can be ascribed to nanoscale ferroelectric domain at room temperature for BNT-0.02VTi, which is induced by chemical disorder and strong random field as VTi generated. Hence, the results imply that the B-site deficiency in BNT is a very effective route to tailor the stability of electrically induced long-range ferroelectric order.
关键词： depolarization,B-site deficiency,Bi0.5Na0.5TiO3,ferroelectric properties,relaxor transition
更新于2025-09-04 15:30:14
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Ferromagnetic, Ferroelectric and Optical Modulated Multiple Resistance States in Multiferroic Tunnel Junctions
摘要： In data storages, spin, ferroelectric or optical index has been utilized as the information carrier, and the binate couplings among the three parameters are explored to increase the resistance states and resultant data-density. However, studies holding all of the three information indices are still blank, where the risen number of information carriers from previous two to three provides opportunities for inducing novel phenomena and distinct resistance states. In this work, using the spin-electron-photon resolved theory, we demonstrate the feasibility of spin, ferroelectric and optical interactions, which are further detected by a spin- and ferroelectric-modulated photovoltaic effect in La2/3Sr1/3MnO3/BiFeO3/Fe4N multiferroic tunnel junctions (MFTJs). Moreover, on the basis of spin- and ferroelectric-induced four resistance states in MFTJs, the special photovoltaic effect shall split each resistance state into the light-on and light-off switching states, which finally leads to the multiple resistance states. Besides, nearly 100% spin-polarized photocurrent and large tunneling magnetoresistance (electroresistance) are realized in this MFTJs. These results reveal that interacted spin, ferroelectric and optical indices can simultaneously serve as information carriers in storages, which provide guidance for developing efficient data memories.
关键词： Photovoltaic,La2/3Sr1/3MnO3,Ferroelectric,Spin,Fe4N,BiFeO3
更新于2025-09-04 15:30:14
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Preparation and Characterization of Ba1-xSrxTiO3 by Sol-Gel Method
摘要： Barium strontium titanate (BST) with formula (Ba1-xSrxTiO3) has been synthesized by sol-gel method with different stoichiometric compositions (x = 0.3, 0.4, 0.5, 0.6). The raw materials which used to prepare compounds are (Ba,Sr) acetate as a source (Ba,Sr) and titanate isopropoxide source. The FE-SEM images showed that the particles size reduced from 464 to 13 nm when strontium concentration increased from 0.3 to 0.6. The X-ray diffraction studies have confirmed that Ba0.7Sr0.3TiO3 sample have the tetragonal phase while remaining samples have a cubic phase. The intensity of the major peaks were decreased and shifted toward higher 2θ angles when Sr2+ ions increases.
关键词： Barium strontium titanate,Curie Temperature,Ferroelectric materials,Perovskite structure
更新于2025-09-04 15:30:14
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Piezotronic modulations in electro- and photochemical catalysis
摘要： Electrochemical catalyst design and optimization primarily relies on understanding and facilitating interfacial charge transfer. Recently, piezotronics have emerged as a promising method for tuning the interfacial energetics. The unique band-engineering capability using piezoelectric or ferroelectric polarization could lead to performance gains for electrochemical catalysis beyond what can be achieved by chemical or structural optimization. This article addresses the fundamentals of surface polarization and corresponding band modulation at solid–liquid interfaces. The most recent advances in piezotronic modulations are discussed from multiple perspectives of catalysis, including photocatalytic, photoelectrochemical, and electrochemical processes, particularly for energy-related applications. The concept of piezocatalysis, a direct conversion of mechanical energy to chemical energy, is introduced with an example of mechanically driven water splitting. While still in the early stages, piezotronics is envisioned to become a powerful tool for revolutionizing electrochemical catalysis.
关键词： electrochemical catalysis,piezotronics,piezoelectric polarization,piezocatalysis,ferroelectric polarization
更新于2025-09-04 15:30:14
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Integration of sputter-deposited multiferroic CoFe2O4-BiFeO3 nanocomposites on conductive La0.7Sr0.3MnO3 electrodes
摘要： The structure, magnetic and ferroelectric properties of sputtered epitaxial CoFe2O4-BiFeO3 (CFO-BFO) nanocomposite thin films grown on La0.7Sr0.3MnO3 (LSMO) layers on (001) oriented SrTiO3 (STO) substrates and on STO-buffered Si are described. The as-grown LSMO thin films were smooth and poorly conductive but the resistivity was reduced and the surfaces roughened after annealing. Cosputtered CFO and BFO on STO formed vertically aligned nanostructures consisting of epitaxial spinel CFO pillars within a perovskite BFO matrix, but the rough surface of the annealed LSMO film promoted additional CFO pillar orientations. A reorientation of the CFO magnetic easy axis to an in-plane direction occurred as the LSMO became thicker due to changes in the strain state of the CFO pillars. The LSMO underlayer enabled the ferroelectric response of the BFO to be measured. Nanocomposites were grown onto LSMO/SrTiO3/Si which provides a path towards large scale integration of electrically contacted nanocomposites on Si.
关键词： La0.7Sr0.3MnO3,sputter-deposited,ferroelectric,magnetic properties,nanocomposites,CoFe2O4-BiFeO3,multiferroic
更新于2025-09-04 15:30:14
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Strain-Mediated Substrate Effect on the Dielectric and Ferroelectric Response of Potassium Sodium Niobate Thin Films
摘要： If piezoelectric thin films sensors based on K0.5Na0.5NbO3 (KNN) are to achieve commercialization, it is critical to optimize the film performance using low-cost scalable processing and substrates. Here, sol–gel derived KNN thin films are deposited using a solution with 5% of potassium excess on Pt/TiO2/SiO2/Si and Pt/SrTiO3 substrates, and rapid thermal annealed at 750 ?C for 5 min. Despite an identical film morphology and thickness of ~335 nm, an in-plane stress/strain state is found to be tensile for KNN films on Pt/TiO2/SiO2/Si, and compressive for those on Pt/SrTiO3 substrates, being related to thermal expansion mismatch between the substrate and the film. Correspondingly, KNN films under in-plane compressive stress possess superior dielectric permittivity and polarization in the parallel-plate-capacitor geometry.
关键词： stress/strain,ferroelectric hysteresis,dielectric properties,KNN thin films,sol–gel,thermal expansion
更新于2025-09-04 15:30:14
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Ferroelectric properties of Ag doped PbZr0.53Ti0.47O3 thin film deposited by sol–gel process
摘要： To suppress the generation of oxygen vacancy during the PbZr0.53Ti0.47O3 (PZT) film synthesis process, herein, the 0–3 type Ag/PZT film is chosen as a prototype to systematically investigate the mechanisms of oxygen vacancy decrease and the relationship of ferroelectric properties. The uniform and dense films were successfully fabricated on fluorine tin oxide glasses (FTO) by facile sol–gel processes. It is confirmed the existence of silver nanoparticles in the film, indicating the composite ferroelectric films are of 0–3 type. When Ag doping mole concentration is 0.010 in the sol, a large remnant polarization (Pr) of ~ 50.7 μΧ/cm2 is got, which is 37.9 μΧ/cm2 for pure PZT. UV–vis spectrum confirms the generation of Ag2O in the process of mixing the sol. Furthermore, the oxygen vacancies caused by natural evaporation of lead specie are effectively reduced because of the decomposition of Ag2O, confirmed by X-ray photoelectron spectroscopy. This work points out the generated Ag2O as the intermediate product is the key to achieve high remnant polarization in Ag/PZT based film and make it as a promising candidate for memory applications.
关键词： remnant polarization,oxygen vacancy,Ag doped PbZr0.53Ti0.47O3,sol–gel process,Ferroelectric properties
更新于2025-09-04 15:30:14