- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2019
- 2018
- 2017
- MPPT
- photovoltaic (PV) power systems
- Induction motor
- three-phase four switch inverter
- two-inductor boost converter
- Optical pattern
- Phase diagram
- Surfactants
- rad-hard
- converter
- Electrical Engineering and Automation
- Optoelectronic Information Science and Engineering
- Chemistry
- ETRI
- Inner Mongolia University
- Universiti Malaysia Terengganu
- Virginia Tech
- Indian Institute of Technology Indore
- Sree Buddha College of Engineering
- Devi Ahilya University
- GCoE, Amravati
- VPT, Inc.
- Beihang University
-
Evolving antiferroelectric stability and phase transition behavior in NaNbO3-BaZrO3-CaZrO3 lead-free ceramics
摘要： The stability of antiferroelectricity in NaNbO3 ceramics was found to evolve with co-doping x mol% CaZrO3 and 6 mol% BaZrO3, from a dominant ferroelectric (FE) orthorhombic Q phase (x=0) to a gradually stabilized antiferroelectric (AFE) orthorhombic P phase owing to different ionic radii of Ba and Ca ions. Although a complete AFE P phase appears at x=0.5, the field induced AFE-FE phase transformation is irreversible at first, and then becomes partially reversible at x=1 and finally completely reversible at x=3. The above-mentioned change process proves to be associated with the enhancing stability of antiferroelectricity with x, as evidenced by means of dielectric, polarization and strain properties as well as in/ex-situ synchrotron x-ray diffraction and Raman spectra. A composition-field phase diagram for the NN-based lead-free AFE ceramic was constructed on basis of the phase structural change, which would provide a clear understanding of how ion doping influences its antiferroelectricity.
关键词： lead-free ceramics,Antiferroelectricity,phase transition,NaNbO3
更新于2025-11-14 17:28:48
-
Significantly enhanced room temperature electrocaloric response with superior thermal stability in sodium niobate-based bulk ceramics
摘要： Converting electrical into thermal energy in ferroelectrics path the way for a novel cooling technology, be able to open up new fields of applications. For electrocaloric refrigeration, large temperature change (ΔT) and excellent temperature stability are highly desired. Unfortunately, a large room temperature ΔT in lead free bulk ceramics was usually obtained at the expense of temperature stability, and vice versa, limiting their practical applications. In this work, composition engineering is carried out as an important strategy to tune phase transition to room temperature and simultaneously induce diffuse phase transition to achieve excellent temperature stability. A large room temperature ΔT is realized by the application of large electric fields, possibly due to the optimization of the sintering process in sodium niobate based ceramics. The 0.78NaNbO3-0.22BaTiO3 ceramic is found to exhibit both large room temperature ΔT (~ 0.70 K) and superior temperature stability (±1.4% variation in ΔT from 300 K to 380 K). Those properties are superior to previously reported lead-free bulk ceramics. This work provides a guideline for the development of high-performance ceramic materials such as NaNbO3-ABO3 (A=Ba, Sr and Ca; and B=Ti and Zr) for electrocaloric refrigeration. Most importantly, this work expands the applications of NN-based ceramics from electric energy storage, electrostrictive and piezoelectric applications, to a new field, i.e. solid-state refrigeration. This makes NN-based ceramics very promising multifunctional materials for device integration.
关键词： Sodium niobate,relaxor ferroelectrics,electrocaloric effect,adiabatic temperature change,diffuse phase transitions
更新于2025-11-14 17:28:48
-
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
-
High electromechanical strain properties in SrTiO3?modified Bi1/2Na1/2TiO3?KTaO3 lead?free piezoelectric ceramics under low electric field
摘要： This study investigated the structures, dielectric, ferroelectric and piezoelectric properties of (0.99?x)Bi1/2Na1/2TiO3?0.01KTaO3?xSrTiO3 (BNT?KT?100xST, x = 0.20 ~ 0.235) lead?free piezoelectric ceramics. These piezoceramics were synthesized by conventional solid?state reaction method. As a consequence, a large electrical strain and normalized strain (d33* ≈ 793 pm/V) can be obtained even under 3 kV/mm as low electric field for BNT?KT?22.5ST ceramics. The phase transition between nonergodic relaxor (NER) and ergodic relaxor (ER) under electric field might be responsible for its large strain. It means that BNT?KT?100xST lead?free ceramics can be a promising candidate for actuator applications.
关键词： Phase transition,Lead-free,Ternary system,Piezoelectric ceramics,Relaxor
更新于2025-11-14 17:28:48
-
Phase-transition induced giant negative electrocaloric effect in a lead-free relaxor ferroelectric thin film
摘要： Ferroelectric/antiferroelectric thin/thick films with large positive or negative electrocaloric (EC) effects could be very useful in designing commercial refrigeration devices. Here, a giant negative EC effect (maximum ΔT ≈ ?42.5 K with ΔS ≈ ?29.3 J K?1 kg?1) comparable to the best positive EC effects reported so far is demonstrated for 0.5(Ba0.8Ca0.2)TiO3–0.5Bi(Mg0.5Ti0.5)O3 (BCT–BMT) lead-free relaxor ferroelectric thin films prepared on Pt(111)/TiOx/SiO2/Si substrates using a sol–gel method. An electric-field induced structural phase transition (nanoscale tetragonal and orthorhombic to rhombohedral) along the out-of-plane [111] direction plays a very key role in developing the giant negative EC effect. This breakthrough will pave the way for practical applications of next-generation refrigeration devices with high cooling efficiency in one cycle by ingeniously utilizing and combining both the giant negative and positive EC effects. Moreover, a large energy density of 51.7 J cm?3 with a high power density of 1.15 × 1010 W kg?1 at room temperature is also achieved in the thin film, indicating that it is also an attractive multifunctional material for energy storage.
关键词： lead-free,energy storage,electrocaloric effect,phase transition,thin film,relaxor ferroelectric
更新于2025-11-14 17:28:48
-
Elastic Properties and Fracture Behaviors of Biaxially Deformed, Polymorphic MoTe <sub/>2</sub>
摘要： Biaxial deformation of suspended membranes widely exists and is used in nanoindentation to probe elastic properties of structurally isotropic two-dimensional (2D) materials. However, elastic properties and particularly fracture behaviors of anisotropic 2D materials remain largely unclarified in the case of biaxial deformation. MoTe2 is a polymorphic 2D material with both isotropic (2H) and anisotropic (1T’ and Td) phases, thereby an ideal system of single-stoichiometric materials to study these critical issues. Here we report the elastic properties and fracture behaviors of biaxially-deformed, polymorphic MoTe2, by combining temperature-variant nanoindentation and first-principles calculations. It is found that due to similar atomic bonding, the effective moduli of the three phases deviate by less than 15 %. However, the breaking strengths of distorted 1T’ and Td phases are only half the value of 2H phase due to their uneven distribution of bonding strengths. Fractures of both isotropic 2H and anisotropic 1T’ phases obey the theorem of minimum energy, forming triangular and linear fracture patterns, respectively, along the orientations parallel to Mo-Mo zigzag chains. Our findings not only provide a reference database for the elastic behaviors of versatile MoTe2 phases, but also illuminate a general strategy to the mechanical investigation of any isotropic and anisotropic 2D materials.
关键词： elastic properties,phase transition,MoTe2,nanoindentation
更新于2025-11-14 17:04:02
-
Controllable preparation of phase-separated Pb/Zn heterogeneous nanoparticles by laser ablation and their application in the growth of PbS tipped ZnS nanorods heterostructures
摘要： Phase-separated Pb/Zn heterogeneous nanoparticles (Pb/Zn HNPs) with a controllable phase ratio were firstly prepared by long-pulse-width millisecond laser ablation of Pb/Zn binary metal target immersed in anhydrous ethanol under room conditions. The phase ratio in the as-ablated Pb/Zn HNPs was mainly determined by the molar ratio of Pb/Zn in the initial binary metal target and the structure of Pb/Zn HNPs was partly influenced by the pulse laser width. Then the PBS tipped ZnS nanorods heterostructures (PbS/ZnS heterostructures) were grown by simply heating the mixture of the as-ablated Pb/Zn HNPs and thioacetamide (TAA) at 450 (cid:1)C in a tube furnace. The size and morphology of Pbs/ZnS heterostructures were decided by the original absolute size and relative size between phase-separated Pb and Zn nanoparticle. The formation of Pbs/ZnS heterostructures was the result of the diffusion-limited of S atoms in the Pb/Zn HNPs. This study not only provides a new strategy for the controllable preparation of phase-separated bimetallic nanoparticles that can be used for the growth of specific heterostructures but a new view on the fundamental physical and chemical aspects of nanocrystal formation after laser ablation of solids in liquids.
关键词： Heterostructure,Phase-separated,Heterogeneous nanoparticles,Laser ablation,Binary metal target,Diffusion-limited
更新于2025-11-14 17:04:02
-
Mechanical analysis of the interface bonding state of a TiO2 film/Si substrate
摘要： TiO2 film is prepared on the surface of a natural oxide layer of a monocrystalline silicon substrate via RF magnetron sputtering. HRTEM (High Resolution Transmission Electron Microscope) imaging and EDX spectroscopy are performed on the sample interface, demonstrating that the film sample has a two-layer structure. Combined with XRD, the analysis shows that the upper film is a crystalline TiO2 film with a thickness of approximately 30 nm and that the lower film is a natural amorphous SiO2 oxide film with a thickness of approximately 22 nm. A geometric phase analysis (GPA) and Hooke's law are used to analyse the stress and bonding state at the interfaces between the monocrystalline silicon substrate and the natural oxide layer, between rutile TiO2 and the natural oxide layer, and between anatase TiO2 and the natural oxide layer. It is concluded that the interface bonding state of the monocrystalline silicon/natural oxide layer is good and that the interface bonding state at the interface between rutile and the natural oxide layer is better than that between anatase and the natural oxide layer.
关键词： geometric phase analysis,Hooke's law,natural oxidation,interface bonding states,TiO2
更新于2025-11-14 17:04:02
-
<p>A multifunctional-targeted nanoagent for dual-mode image-guided therapeutic effects on ovarian cancer cells</p>
摘要： Nanomedicine has emerged as a novel therapeutic modality for cancer treatment and diagnosis. Lipid–polymer hybrid nanoparticles (LPHNPs) are core–shell nanoparticle (NP) structures comprising polymer cores and lipid shells, which exhibit complementary characteristics of both polymeric NPs and liposomes. However, it is difficult to wrap perfluoropentane (PFP) into core–shell NPs in the existing preparation process, which limits its application in the integration of diagnosis and treatment. Methods: The folate-targeted LPHNPs-loaded indocyanine green/PFP-carrying oxygen (TOI_HNPs) using a combination of two-step method and solution evaporation technique for the first time. The essential properties and dual-mode imaging characteristics of developed NPs were determined. The cellular uptake of TOI_HNPs was detected by confocal microscopy and flow cytometry. The SKOV3 cell viability and apoptosis rate were evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and flow cytometry. The ROS was demonstrated by fluorescence microplate reader and the expression of hypoxia-inducible factor 1-alpha (HIF-1α) and IL-6 was detected by Western blot. Results: TOI_HNPs showed spherical morphology with particle size about (166.83±5.54) nm and zeta potential at -(30.57±1.36) mV. It exhibited better stability than lipid NPs and higher encapsulation efficiency as well as active targeting ability than poly (lactic-co-glycolic acid) (PLGA) NPs. In addition, the novel NPs could also act as the contrast agents for ultrasound and photoacoustic imaging, providing precision guidance and monitoring. Furthermore, TOI_HNPs-mediated photo–sonodynamic therapy (PSDT) caused more serious cell damage and more obvious cell apoptosis, compared with other groups. The PSDT mediated by TOI_HNPs induced generation of intracellular ROS and downregulated the expression of HIF-1α and IL-6 in SKOV3 cells. Conclusion: This kind of multifunctional-targeted nanoagent may provide an ideal strategy for combination of high therapeutic efficacy and dual-mode imaging guidance.
关键词： core-shell nanoparticle,ultrasound,photo-sonodynamic therapy,phase transformation,photoacoustic imaging,laser
更新于2025-11-14 17:03:37
-
The effect of second phase La0.67TiO2.87 on the phase structure and impedance spectroscopy of La2Ti2(1 + x)O7 piezoelectric ceramics
摘要： The Ti excess La2Ti2 (1 + x) O7 (x = 0, 0.005, 0.01, 0.02, 0.05, 0.1) piezoelectric ceramics have been prepared by sol-gel technology and solid state synthesis method. Through refinement analysis, the phase structure of the ceramics varies with Ti content. Most monoclinic phase (~ 93 %) and a handful of orthogonal phase (~ 7 %) coexist in La2Ti2 (1 + 0) O7 ceramics. Pure monoclinic phase La2Ti2O7 with space group P21 appears in La2Ti2 (1 + 0.005) O7 and La2Ti2 (1 + 0.01) O7 ceramics. Monoclinic phase La2Ti2 O7 and a certain proportion of tetragonal phase La0.67TiO2.87 coexist in La2Ti2 (1 + 0.02) O7, La2Ti2 (1 + 0.05) O7 and Ti2 (1 + 0.1) O7 ceramics. With the excess of Ti content, the monoclinic phase ratio and distortion angles in a-b projection plane of the ceramics increase first and then decrease, which is consistent with the variation tendency of piezoelectric constant d33. The excellent piezoelectric constant for Ti2 (1 + 0.01) O7 ceramics is 2.8 pC/N. Impedance analysis shows that the conductive mechanisms of all samples include both grain and grain boundary conductivity at temperature range T ≥ 500 ℃. The formation of tetragonal phase La0.67TiO2.87 derives from Ti excess in pure monoclinic phase La2Ti2O7. The existence of tetragonal phase La0.67TiO2.87 can obviously increase the capacitance of ceramics at x ≥ 0.05. All prepared piezoelectric La2Ti2 (1 + x) O7 ceramics have highly frequency stability and are candidates for ultrahigh temperature piezoelectric application.
关键词： La2Ti2(1 + x)O7 ceramics,phase structure,impedance spectroscopy
更新于2025-11-14 15:27:09