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[Lecture Notes in Mechanical Engineering] Advances in Thin Films, Nanostructured Materials, and Coatings (Selected Papers from the 2018 International Conference on “Nanomaterials: Applications & Properties”) || Stain Effect on the Properties of Polar Dielectric Thin Films
摘要： Low cost scalable processing and substrates are critical for optimized polar dielectric performance of functional oxide thin ?lms if they are to achieve commercialization. Here, we present a comprehensive investigation of the role low-cost MgO, Al2O3, SrTiO3 and Si substrates on the structural and electrical properties of sol-gel derived SrTiO3 (ST) and K0.5Na0.5NbO3 (KNN) thin ?lms. The substrate is found to have a strong effect on the stress/stain state and, consequently, on the dielectric and ferroelectric response of the ?lms. A tensile stress induced in-plane by the thermal expansion mismatch between the substrates and the ?lms observed for ST and KNN ?lms deposited on platinized Al2O3 and Si substrates, respectively, lowers the relative permittivity and remanent polarization values in the parallel plate capacitor geometry. In contrast, a compressive stress/strain observed for ST ?lms deposited on MgO/Pt and KNN ?lms on SrTiO3/Pt substrates result in superior polarization and dielectric permittivity, corresponding to enhanced out-of-plane displacement of Ti4+ ions in ST ?lms and Nb5+ ions in KNN ?lms. It is thus demonstrated that for polycrystalline polar dielectric thin ?lms the relative permittivity and polarization may be optimized through an induced compressive stress state.
关键词： Dielectric properties,Sol-gel,Thin ?lms,Stress/strain,Thermal expansion,Ferroelectric hysteresis
更新于2025-11-14 17:28:48
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Effect of BaZr <sub/>0.4</sub> Ti <sub/>0.6</sub> O <sub/>3</sub> addition on electrical and magnetic properties of multiferroic (1-x)BiFeO <sub/>3</sub> -xBaTiO <sub/>3</sub> ceramics
摘要： The 0.75((1-x)BiFeO3-xBaTiO3)-0.25BaZr0.4Ti0.6O3 or 0.75(BFO-BTO)-0.25BZT ceramics (x = 0.23–0.27) have been prepared by solid state reaction method to studied the relationship between phase formation, dielectric and magnetic properties. The results found that the phase formations of calcined BFO-BTO and BZT powders are distorted rhombohedral and cubic structure, respectively. Moreover, the addition of BZT in BFO-BTO-BZT ceramics affected to the phase change dramatically according to increasing of BZT content compared to calcined BFO-BTO powders. All the samples showed cubic perovskite structure. The room temperature dielectric properties decreased with increasing of BTO content, the highest dielectric constant with low losses observed in 0.75(0.77BFO-0.23BTO)-0.25BZT ceramic. Furthermore, the ceramics displayed maximum dielectric constant temperature (Tm) above 360 °C. Interestingly, all ceramic compositions exhibited typical ferromagnetic hysteresis loop and the highest remanent magnetization observed in 0.75(0.77BFO-0.23BTO)-0.25BZT ceramic.
关键词： composite,dielectric properties,ferromagnetic hysteresis loops,BFO-BTO,BZT
更新于2025-11-14 17:28:48
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Temperature-dependent phase transition in [001]-oriented 0.72Pb(MgNb)O-0.28PbTiO single crystals
摘要： Temperature-dependent dielectricity and polarization of [001]C-oriented 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 relaxor-based ferroelectric single crystals were studied by using a combined method of the X-ray di?raction, dielectric spectrum, polarization-electric (P-E) ?eld hysteresis loops, and the Landau-phenomenological theory. Results show that the room-temperature rhombohedral phase experiences a rhombohedral-monoclinic-tetragonal coexisting state, then transforms to tetragonal phase, and ?nally to cubic phase during the zero-?eld-heating process. The six-order Landau-type thermal expansion parameters for the tetragonal phase were determined by using the typical characteristics at the cubic-tetragonal phase transition in the temperature range from 91 °C to 113 °C. The calculated dielectric curve, polarizations, and P-E loops ?t well with the experimental results. The phase stability and piezoelectricity are further studied and compared with those of the PMN-0.36PT single crystal. The provided methods and obtained Landau parameters can be used for further studies on the relaxor-based ferroelectric single crystals.
关键词： PMN-PT single crystals,Phase transition,Double hysteresis loops,Landau expansion parameters
更新于2025-11-14 17:28:48
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Investigation of Fe-doped room temperature dilute magnetic ZnO semiconductors
摘要： Different ceramics sample of Zn1-xFexO (ZFO) series have been sintered by solid state reaction method. Single phase polycrystalline Fe-doped ZnO sample with hexagonal wurtzite structure has been obtained with x < 0.03 mol. Segregation of Fe and/or its oxides have not been found in the XRD patterns. A weak secondary phase of ZnFe2O4 has been detected with x ≥ 0.03 mol. Presence of Ohmic conductivity has been detected in the dielectric property analysis and the reasons for this Maxwell-Wagner-Sillars (MWS) relaxation has been explained by the grain boundary barrier defect (GBBD) process. The obtained shift of diamagnetic behavior of pure ZnO samples to para-magnetic for ZFO samples has been established with the defect and impurity structure. The band gap energy for ZFO samples has been calculated between 2.85 eV to 3.15 eV. The results indicate the potential use of Fe doped ZnO ceramics in high frequency device applications.
关键词： Spintronics,XRD,Hysteresis loops,Dilute magnetic semiconductor,Dielectric constant,Optical property
更新于2025-10-22 19:40:53
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Study on Charge transportation and scaling behavior of CsPbI3 microwires
摘要： Cesium lead iodide (CsPbI3) has been prepared by a new experimental hazard free precipitation technique. X-ray diffraction spectra have been interpreted with Rietveld refinement which assures the orthorhombic phase of CsPbI3. Energy dispersive X-ray fluorescence spectra confirms the formation of ternary compound. Orthorhombic to cubic phase transition has been studied by observing hysteresis loop in R(T)-T plot for forward-reverse temperature scan. The intra-grain and inter-grain contribution of CsPbI3 to dielectric relaxation has been accounted by fitting the complex impedance plot (Cole-Cole plot). The value of FWHM in Z″(ω)-lnf or M″(ω)-lnf plot is greater than 1.141 decades which reveals the non-Debye type relaxation within material. The broad relaxation peak signifies that there is a distribution of relaxation time over a mean value. Moreover, Z″ & M″ have been plotted in scaled coordinate to check whether the distribution of relaxation time is temperature dependent or not. The frequency dependent relative permittivity represents the decreases of polarizations with frequency which have been successfully analyzed by Koop’s theory. Here, activation energies are equal for different formalism, suggests that the same type charge carriers involved in conduction as well as relaxation process. Ac conductivity has been interpreted by using Jonncher’s power law and frequency exponent (n) increases with temperature which suggests the presence small polaron hopping mechanism.
关键词： Joncher’s power law,dielectric relaxation,Rietveld,Hysteresis,Cole-Cole plot,CsPbI3 micro-wire
更新于2025-09-23 15:23:52
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Synthesis of Eu2O3 doped BaO-TiO2-GeO2 based glass-ceramics: Crystallization kinetics, optical and electrical properties
摘要： Eu3+ doped transparent glass-ceramics (GCs) containing non-centrosymmetric ferroelastic Ba2TiGe2O8 (BTG) crystals as the major crystalline phase have been synthesized. BTG crystal phase was generated in the glass matrix with mole percent composition 30BaO-15TiO2-55GeO2 synthesized by melt quenching technique followed by controlled crystallization through ceramming heat-treatment. A di?usion controlled surface crystallization event with zero and constant nucleation rates was determined through a comparative study of some linear and nonlinear solid state reaction models. Nonlinear crystallization kinetics studies facilitated determination of the experimental ceramization temperature and time for fabrication of transparent glass-ceramics containing BTG nanocrystals. XRD, FTIR, TEM and FESEM measurements con?rmed the dispersion of BTG nanocrystals of size 20–100 nm in the glass matrix. Local crystal environment around Eu3+ ions facilitated the enhancement of photoluminescence of glass-ceramics with respect to the precursor glass. High dielectric constant, low loss and dissipation factors were observed for the GCs.
关键词： Refractive index,Glass-ceramics,Photoluminescence,Dielectric properties,Crystallization kinetics,Hysteresis loop
更新于2025-09-23 15:23:52
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An Efficient Technique using Modified p-q Theory for Controlling Power Flow in a Single-Stage Single-Phase Grid-Connected PV System
摘要： In this paper, an efficient power conditioning unit (PCU) is presented for a single-phase grid-connected photovoltaic system (GCPVS) incorporating both maximum power-point tracking (MPPT) and current control algorithms in a single-stage. Modified p-q theory is applied to derive the reference signal for a hysteresis band current (HBC) controller so that independently the active and reactive power sharing between the photovoltaic (PV) system and the grid can be controlled. Enhanced stability during the internal dynamics, caused by the variations in PV generation and load conditions, is the prime aspect of the controller. The performance of the proposed p-q theory correlated HBC controller is evaluated against tracking of maximum PV power and compensation of load reactive power under the changeable atmospheric and load conditions, and also compared with the widely used conventional proportional resonant (PR) controller to justify superiority. Simulation and experiment are carried-out under variable weather and different load conditions to validate acceptability of the proposed control scheme.
关键词： modified p-q theory,Single-stage,hysteresis band current (HBC) controller,grid-connected photovoltaic system (GCPVS),power flow controlling
更新于2025-09-23 15:23:52
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A Simplified Approach for Obtaining Optical Properties of VO <sub/>2</sub> Thin Films, and Demonstration of Infrared Shape-Shifting Devices
摘要： Micrometer-sized VO2-based devices with integrated resistive heaters of different configurations are fabricated. Quality of the VO2 films is confirmed by measuring the characteristic drop in transmittance and negative differential emissivity for these films. A two-interface model for optical transmittance, reflectance, and absorbance is presented. This method and analytic model presents an advantage over most typically used approaches in that it does not require direct measurements of the material’s optical constants to estimate transmittance. By combining the substrate and the VO2 film into one layer with a reduced optical admittance, the two-interface model is reduced to a single-layer model. Moreover, the present work demonstrates the implementation of the developed VO2-based devices in adaptive camouflage and shape-converting applications. Electrical pulses are used to program different emissivity states to convert geometric shapes inside a fully integrated VO2-based electro-optical window. This results in the reconfiguring of thermal images to either create new shapes, or shift from one to another.
关键词： shape-configuration,hysteresis,programming states,phase-change materials,smart materials
更新于2025-09-23 15:23:52
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Magnetostrictive effect in micro-dotted FeCo film coated surface acoustic wave devices
摘要： The magnetostrictive effect in micro-dotted FeCo film coated surface acoustic wave (SAW) devices was demonstrated by solving coupling equations using the specific coupling of modes parameters extracted by FEM analysis. Dotted-pattern on FeCo thin-film proposed in this work contributes well to suppression in hysteresis effect by fully releasing the internal coericivity of the magnetistrictive FeCo thin-film. The theoretical demonstration was confirmed well by characterizing the constructed SAW magnetic devices with FeCo dots depositing along the SAW propagation path. Significantly improvements on suppression of hysteresis phenomenon were observed by characterizing the prepared FeCo dots coated SAW magnetic devices, higher magneto-sensitivity of 21.17 kHz mT?1, and lower hysteresis error of 0.82% were achieved successfully.
关键词： magnetostrictive effect,coupling of modes,hysteresis,micro-dotted FeCo film,SAW magnetic device
更新于2025-09-23 15:23:52
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Analysis of a Fractal Josephson Junction with Unharmonic Current-Phase Relation
摘要： In this paper, a fractal Josephson junction with unharmonic current-phase relation is analytically and numerically analyzed. This system has two, four, or no equilibrium points depending on the external direct current source and unharmonic parameter. The stability analysis of the equilibrium points is carried out. The inclusion of unharmonic current-phase relation in an ideal Josephson junction leads to an increase in the hysteresis of current-voltage characteristics. While the inclusion of fractal characteristics in insulating layer of Josephson junction with harmonic current-phase relation leads to a decrease in the hysteresis of current-voltage characteristics. The inclusion of unharmonic current-phase relation on a fractal Josephson junction leads to an increase in the hysteresis of current-voltage characteristics. The dynamical behavior map of fractal Josephson junction with unharmonic current-phase relation in amplitude and frequency of modulation current plane is depicted. For a suitable choice of modulation parameters of external current source, fractal Josephson junction with unharmonic current-phase relation can exhibit excitable mode, bistable oscillatory mode, and periodic and chaotic behaviors.
关键词： Current-voltage characteristics,Unharmonic current-phase relation,Fractal Josephson junction,Bistability,Chaotic behavior,Hysteresis
更新于2025-09-23 15:23:52