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Liquid Crystals - Self-Organized Soft Functional Materials for Advanced Applications || Binary Mixture Composed of Nematic Liquid Crystal and Carbon Nanotubes: A Theoretical Description
摘要： Based on the phenomenological model first presented by van der Schoot et al., which predicts the alignment of carbon nanotube (CNT) dispersions in thermotropic nematic liquid crystals, we present the extensive results concerning the phase diagram and the orientational properties of the mixture in this chapter.
关键词： phase transition,liquid crystal,carbon nanotube
更新于2025-09-23 15:23:52
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Large electric field-induced strain in ternary Bi0.5Na0.5TiO3-BaTiO3-Sr2MnSbO6 lead-free ceramics
摘要： The large electric-field-induced strain of Bi0.5Na0.5TiO3-BaTiO3 based ceramic make it a potential replacement for lead-based ferroelectrics in actuator applications. Herein, a ternary system (1-x)(Bi0.5Na0.5)0.935Ba0.065TiO3-xSr2MnSbO6 (BNBT6.5-xSMS) ceramic was fabricated using conventional solid-state reaction. It was found that the ferroelectric to relaxor phase transition temperature TF-R gradually shifted to lower temperature by increasing SMS contents. The ferroelectricity and piezoelectricity of BNBT6.5 were highly affected by trace amount of SMS doping. For composition BNBT6.5-0.003SMS, where TF-R was near room temperature, a large electric-field-induced unipolar strain of ~0.4% with high normalized strain (Smax/Emax) of 728 pm/V, which is comparable to lead-based ferroelectric/antiferroelectric ceramics, was achieved owing to the reversible electric-field-induced phase transition between a non-polar relaxor phase to a polar phase with long-range ferroelectric order.
关键词： electric-field-induced phase transition,ferroelectric,Lead-free ceramics,Bi0.5Na0.5TiO3
更新于2025-09-23 15:23:52
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Magnetic, magneto-optical and specific heat studies of the low temperature anomalies in the magnetodielectric DyIG ferrite garnet
摘要： Measurements of magnetization and Cotton Mouton effect (CM) under external magnetic field (Hex) combined with specific heat experiments at Hex = 0, were performed on dysprosium iron garnet Dy3Fe5O12 (or DyIG) single crystals. From the low-temperature dependences of some magnetic, magneto-optical and thermodynamic quantities, such as spontaneous magnetization, both magnetic and CM susceptibilities and the excess specific heat due to the contribution of Dy3+ ions only, give rise to the appearance of two types of anomalies. The first one which is related to the ‘low temperature paraprocess’ effect, occurs in the region of the ‘Belov point’ TB predicted at 42 K. Whereas the second one, which is due to the previous spin reorientation transition, takes place at TSR = 15 K. The easy axis of magnetization which remains along the <111> direction above TSR, changes spontaneously below TSR and becomes aligned along the low symmetry angular <uuw> phases. The results are analyzed taking into account those reported earlier such the negative magnetodielectric effect for Hex < 10 kOe and the Schottky effect which cause anomalies respectively, in the dielectric constant at TSR and in the excess specific heat near the low temperature point TB.
关键词： Low temperature Belov point,Dy3Fe5O12,Ferrimagnetism,Field induced phase transition,Spin reorientation
更新于2025-09-23 15:23:52
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Fascinating Physical Properties of 2D Hybrid Perovskite [(NH3)(CH2)7(NH3)]CuClxBr4?x, x?=?0, 2 and 4
摘要： The 2-D organic–inorganic hybrid perovskites of the formula [(NH3)(CH2)7(NH3)]CuClxBr4?x, x = 0, 2 and 4 were prepared by slow evaporation from ethanolic solution in stoichiometric ratio 1:1 (organic/inorganic). Microchemical analysis and x-ray diffraction (XRD) were used to confirm the formation of the presently investigated hybrids. Differential scanning calorimetry (DSC) indicated order–disorder transitions at T1 = 357 K, T2 = 388 K, and T3 = 398 K for x = 0, 2 and 4 of the three heptane diammonium Cu hybrid perovskites, respectively. These transitions are in good agreement with the electrical permittivity results at different frequencies and temperatures. Optical properties and estimated band gap energy reveal that the band gap energy decreases sharply with replacement of Cl ion by Br ion where the band gap energy of [(NH3)(CH2)7(NH3)]CuBr4, x = 0 (denoted 2C7CuBr) is 1.6 eV (brown color) and for [(NH3)(CH2)7(NH3)]CuCl4, x = 4 (denoted 2C7CuCl) is 2.6 eV (yellow color). The differential magnetic susceptibility of 2C7CuBr in the temperature range 80–300 K indicates the effective magnetic moment μeff = 2.05 BM.
关键词： 2D hybrid perovskite,optical properties of halide perovskite,phase transition,magnetic properties of Cu perovskite
更新于2025-09-23 15:23:52
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Evolution of the infrared emissivity of Ni during thermal oxidation until oxide layer opacity
摘要： The mid-infrared (3–22 μm) emissivity of high-purity Ni has been studied in its pure state, during an isothermal oxidation in air at 730 °C and in the fully oxidized state. Measurements in pure Ni were performed in Ar between 200 and 800 °C and a change of slope in the temperature dependence of the total normal emissivity around its Curie temperature (354 °C) was observed. An oxidation process was carried out at 730 °C for 33 days, when the emissivity stopped evolving and the results were representative of NiO. During the ?rst stages, the emissivity evolved forming the usual interference patterns of semi-transparent ?lms. A mixture of oscillatory and monotonic behaviours of the emissivity as a function of wavelength and oxide layer thickness was found, which manifests as a non-trivial evolution of the total normal emissivity, di?erent than that reported in previous studies. Finally, the emissivity of NiO was measured from below its Néel temperature (252 °C) to 850 °C. It showed the typical shape of a ceramic material with an extra vibrational mode due to two-phonon processes and an additional absorption band around 5 μm in the antiferromagnetic phase produced by magnons. The temperature dependence of its total normal emissivity di?ers signi?cantly from that of a lightly oxidized nickel sample from the literature. Overall, the in?uence of the surface characteristics on the thermal radiative properties of oxidized Ni is thoroughly discussed and highlights the importance of accounting for all possible sources of infrared emissivity evolution in order to make accurate radiative heat transfer calculations.
关键词： Nickel oxide,Infrared emissivity,Radiometry,Radiative heat transfer,Magnetic phase transition,Nickel,Oxidation
更新于2025-09-23 15:23:52
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Quantum phase transition modulation in an atomtronic Mott switch
摘要： Mott insulators provide stable quantum states and long coherence times due to small number fluctuations, making them good candidates for quantum memory and atomic circuits. We propose a proof-of-principle for a 1D Mott switch using an ultracold Bose gas and optical lattice. With time-evolving block decimation simulations—efficient matrix product state methods—we design a means for transient parameter characterization via a local excitation for ease of engineering into more complex atomtronics. We perform the switch operation by tuning the intensity of the optical lattice, and thus the interaction strength through a conductance transition due to the confined modifications of the 'wedding cake' Mott structure. We demonstrate the time-dependence of Fock state transmission and fidelity of the excitation as a means of tuning up the device in a double well and as a measure of noise performance. Two-point correlations via the g(2) measure provide additional information regarding superfluid fragments on the Mott insulating background due to the confinement of the potential.
关键词： quantum gas,atomtronic switch,optical lattice,atomtronics,quantum phase transition,matrix product states,Mott insulator
更新于2025-09-23 15:23:52
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High room-temperature pyroelectric property in lead-free BNT-BZT ferroelectric ceramics for thermal energy harvesting
摘要： Pyroelectrics are attracting increasing attention because they enable pyroelectric generators to extract energy from low-gradient-temperature heat for portable electronic devices. High pyroelectric coefficient around room temperature is essential for high-performance energy harvesters, which, unfortunately, is only commonly achieved in lead-based ferroelectrics. Herein we report a high room temperature pyroelectric response of 27.2 × 10-4 C m-2 K-1 in 0.94(Bi0.5Na0.5)TiO3-0.06Ba(Ti0.75Zr0.25)O3 lead-free ceramics by modulating the Zr4+/Ti4+ ratio to tune the ferroelectric-relaxor antiferroelectric-like phase transition point to around ambient temperature, whose pyroelectric response is one order of magnitude higher than that of the sample without Zr and even comparable to those of lead-containing pyroelectrics. The theoretical analysis revealed that introduced Zr4+ could incorporate into the TiO6 octahedral lattices and break the long-range translational symmetry of BaTiO3 lattices, resulting in the reduction of B-site ion displacement activation energy and transition point of ferroelectric-relaxor antiferroelectric-like phase, giving rise to a pronounced room-temperature pyroelectric effect in BNT-BZT.
关键词： BNT-BZT ceramics,Energy harvesting,Room temperature pyroelectric property,Phase transition
更新于2025-09-23 15:23:52
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Photoinduced collective mode, inhomogeneity, and melting in a charge-order system
摘要： We theoretically investigate photoresponses of a correlated electron system upon stimuli of a pulsed laser light. Real-time dynamics of an interacting spinless fermion model on a one-dimensional chain, as a model of charge order (CO), are numerically simulated using the time-dependent Hartree-Fock method. In particular, we discuss the differences between two situations as the initial state: the homogeneous order and the presence of a domain wall, i.e., a kink structure embedded in the CO bulk. Coherent dynamics are seen in the former case: When the frequency of the pump light ωp is varied, along with single particle excitations across the CO gap (ΔCO), the resonantly-excited collective phase mode near ωp ≈ ΔCO/2 efficiently destabilizes CO. In clear contrast, in the latter case, when ωp is tuned at such in-gap frequencies and the intensity of light is sufficiently large, inhomogeneity spreads out from the kink to the bulk region through kink creations. Moreover, even stronger intensity induces the inhomogeneous melting of CO where the CO gap is destroyed.
关键词： photoinduced phase transition,charge order,collective mode,inhomogeneity,time-dependent Hartree-Fock method
更新于2025-09-23 15:23:52
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The evolution of phase structure, dielectric, strain, and energy storage density of complex-ions (Sr1/3Nb2/3)4+ doped 0.82Bi0.5Na0.5TiO3-0.18Bi0.5K0.5TiO3 ceramics
摘要： Lead-free Bi0.5(Na0.82K0.18)0.5Ti1-x(Sr1/3Nb2/3)xO3 (abbreviated as BNKT-xSN, x = 0.02–0.045) ceramics were fabricated via the conventional ceramic process, and the (Sr1/3Nb2/3)4+ complex-ions were used to modify the phase transition and multifarious electrical responses of BNKT-xSN ceramics. The SN complex-ions absolutely incorporate into the lattice of BNKT matrix to form perovskite structure. The grain morphologies and size are almost unaffected by SN complex-ions. The phase transition concerning ferroelectric type transforming into ergodic relaxor happens with increasing SN content, and the corresponding critical point is x = 0.035. The phase transformation process results in the improvement of energy storage density (W = 0.754 J/cm3) at 80 kV/cm and a high bipolar strain (S = 0.25%) with small hysteresis. The dielectric constant at Tm peaks gradually decreases with increasing SN content, and the ferroelectric-relaxor transition temperature (TF-R) is depressed to room temperature. The evolution behaviors might facilitate our cognition about the mechanism between phase structure and multiple electrical properties of BNT-based ceramics.
关键词： BNT-BKT,(Sr1/3Nb2/3)4+,Phase transition,Field-induced strain,Energy storage
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Bistable Optical Functions of Polyethylene Glycol
摘要： Polyethylene glycol takes both transparent and translucent phases during the phase transition process at around room temperature. This bistability seems useful to create optical devices including 3D displays and tunable random lasers. These devices, however, require a spot-heating technique that controls the phase of each microelement. Self-heating of microelements is achievable if the electric conductivity of the polyethylene glycol is enhanced by the dissolution of alkaline halide salts.
关键词： ionic conduction,bistability,optical functions,polyethylene glycol,phase transition
更新于2025-09-23 15:23:52