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Meso-kinetics of one time relaxation electrical processes in BaTiO <sub/>3</sub> ceramics—modified Boltzmann-Poisson model
摘要： This paper is focused on the research an improved version of the Boltzmann-Poisson model for BaTiO3-ceramics. In the approximation of one relaxation time, for constant external electrical field, this approach included correct quadratic relation for varistor effect in the case of the Heywang model. Within meso-kinetics, quantum corrected Boltzmann-Poisson model, contains space-time correlations for the probability distribution density function f(r, k, t), fractional relaxation velocity description. These new results corresponds to our other research based on electronic particles Brownian motion within its fractal nature.
关键词： Brownian motion,BaTiO3-ceramics,fractals,Heywang model,Boltzmann-Poisson model,dielectrics
更新于2025-09-10 09:29:36
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Structural, Dielectric and Electrical Properties of (1-x)CaCu3Ti4O12?xBaTiO3 Ceramics
摘要： In this work, the effect of BaTiO3 (BT) addition on structural, dielectric and electrical properties of CaCu3Ti4O12 (CCTO) ceramic was investigated. Ceramic samples with the chemical formula (1-x)CaCu3Ti4O12 – xBaTiO3, (1-x)CCTO-xBT, (x = 0.00, 0.10, 0.20, 0.30, 0.50 and 1.00) were synthesized by solid state route. The structural studies carried out by X-ray diffraction technique and showed that the perovskite structure cubic and tetragonal phases were formed without any other impurity phases. The addition of BaTiO3 into CCTO system lowered the last crystallite size to about 52 nm and increased the dielectric constant by four orders compared to pure CCTO. Moreover, the results of the complex impedance analyses of (1-x)CCTO–xBT ceramics samples confirmed the presence of non-Debye type of relaxation phenomenon and exhibited a negative temperature coefficient of resistance behaviour.
关键词： Raman spectroscopy,Barium titanate,Ceramics
更新于2025-09-10 09:29:36
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The origin of enhanced magnetodielectric effect in Y <sub/>3-x</sub> Yb <sub/>x</sub> Fe <sub/>5</sub> O <sub/>12</sub> ceramics
摘要： In this work, dielectric and magnetic behaviors, as well as magnetodielectric (MD) effect of Yb-substituted yttrium iron garnet (Y3-xYbxFe5O12) ceramics, have been studied systematically. Three dielectric relaxations are detected from the temperature spectrums, which can be attributed to the charge carries hopping between Fe2+ and Fe3+, inhomogeneous structure, and conduction, respectively. All the samples exhibit ferrimagnetic behaviors at room temperature and the saturation magnetization (Ms) increases ?rst and then decreases with increasing Yb-substitution. The variation of Ms can be viewed as a comprehensive effect of superexchange interaction of Fe1-O-Fe2 and double exchange interaction between Fe2+ and Fe3+ ions. The room-temperature MD effect of Y3-xYbxFe5O12 ceramics measured at 15 kOe and 1 MHz are ?1.11%, ?1.33%, ?2.04%, ?1.48%, and ?1.57%, for x = 0, 0.5, 1, 2, and 3, respectively. With the analysis of XPS spectra, the origin of enhanced MD effect has been investigated, and it is mainly caused by the response of local dipoles (Fe2+-Fe3+) under applied magnetic ?eld.
关键词： magnetodielectric effect,ferrimagnetic behaviors,Y3-xYbxFe5O12 ceramics,XPS spectra,dielectric relaxations
更新于2025-09-10 09:29:36
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Large electrocaloric effect in tetragonal perovskite 0.03Bi(Mg1/2Ti1/2)O3–0.97(0.875Bi1/2Na1/2TiO3–0.125BaTiO3) lead-free ferroelectric ceramics
摘要： In this work, we reported a large electrocaloric effect (ECE) in tetragonal perovskite 0.03 Bi(Mg1/2Ti1/2)O3–0.97 (0.875Bi1/2Na1/2TiO3–0.125BaTiO3) ceramic. It was found that the composition demonstrates a coexisting state of the ferroelectric P4mm and relaxor P4bm. Due to the ?eld-induced phase transition from relaxor with P4bm symmetry to ferroelectric with P4mm symmetry, a positive ECE is observed in the temperature range of 25–130 °C. Under an electric ?eld of 4 kV/mm, a large temperature change ΔT of 0.75 °C was achieved at 80 °C, and the EC responsivity ΔTmax/ΔE of 0.19 K·cm/kV, indicating a promising lead-free material for potential application in solid-state refrigerators.
关键词： Sodium bismuth titanate,Tetragonal perovskite,Lead-free ceramics,Electrocaloric effect
更新于2025-09-09 09:28:46
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Influence of Sm and Nb on the structural, electric, magnetic and magneto-electric properties of BaTiO3-Li0.5Fe2.5O4 composite ceramics grown by the conventional solid state technique
摘要： The Sm and Nb doped BaTiO3-Li0.5Fe2.5O4 composite ceramics having chemical formulae (90)BaTi(1?2x)NbxSmxO3 + (10) Li0.5Fe2.5O4 (x = 0, 0.05 and 0.1) were synthesized using conventional solid state technique. The structural, morphological, magnetic, dielectric, ferroelectric and magneto-electric properties of composites have been studied. The XRD measurement reveals the absence of peaks pertaining to impurities and strongly confirms the high crystalline nature of all the composites. From FESEM images, the average grain size of composites increases with increase in the concentration of Nb and Sm. The VSM studies confirm the soft magnetic nature of all the composites. The dielectric measurements confirm the increase in the transition temperature (Tc) of the BTL composite with an increase in the concentration of Nb and Sm. The P–E studies confirm that the ferroelectric nature of the BTL composite softens after doping Nb and Sm in it. The ME voltage coefficient value confirms the uniform growth of grains in all the composites and reveals a strong interaction between ferroelectric and magnetic orders.
关键词： magneto-electric properties,BaTiO3-Li0.5Fe2.5O4,electric properties,magnetic properties,composite ceramics,Sm and Nb doping,structural properties
更新于2025-09-09 09:28:46
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The Effect of Textiles Impregnated with Particles of High Emissivity in the Far Infrared, on the Temperature of the Cold Hand
摘要： In engineering and medicine, there is a growing interest in using textiles made of composites with enhanced thermal properties. One such type of textile is fabric impregnated with ceramics and mineral particles. This material has high emissivity in the infrared range and may have therapeutic benefits for treatments of diseases, like Raynaud’s syndrome. While there is significant clinical and commercial interest, there is an evident lack of fundamental studies on the heat transfer aspects of these fabrics. The goal of this technical brief is to presents results from a fundamental study examining the thermal effects of fabric with ceramics and minerals (produced by Nanobionic Inc.) on the temperatures of the hands. With a confidence level of 90%, the results show that the textile with ceramics and minerals has an enhanced thermal effect on warming a cold hand in comparison to a placebo fabric without ceramics or minerals. Much more research is needed to increase the level of confidence and develop an understanding of the thermodynamic mechanism.
关键词： ceramics impregnated textile,infrared emissivity,bioheat transfer
更新于2025-09-09 09:28:46
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Dielectric properties of La/Mn codoped barium titanate ceramics
摘要： La/Mn codoped BaTiO3 ceramics with various La2O3 content, ranging from 0.3 to 1.0 at% La, were investigated regarding their microstructure and dielectric properties. The content of MnO2 was kept constant at 0.01 at% Mn in all samples. La/Mn codoped and undoped BaTiO3 were obtained by a modified Pechini method and sintered in air at 13000C for two hours. The homogeneous and completely fine-grained microstructure with average grain size from 0.5 to 1.5μm was observed in samples doped with 0.3 at% La. In high doped samples, apart from the fine grained matrix, the appearance of local area with secondary abnormal grains was observed. The dielectric properties were investigated as a function of frequency and temperature. The dielectric permittivity of the doped BaTiO3 was in the range of 3945 to 12846 and decreased with an increase of the additive content. The highest value for the dielectric constant at room temperature (εr= 12846) and at the Curie temperature (εr= 17738) were measured for the 0.3 at% La doped samples. The dissipation factor ranged from 0.07 to 0.62. The Curie constant (C), Curie-Weiss temperature (T0) and critical exponent (γ) were calculated using the Curie-Weiss and the modified Curie-Weiss law. The highest values of Curie constant (C=3.27·105 K) was measured in the 1.0 at% La doped samples. The obtained values for γ ranged from 1.04 to 1.5, which pointed out the sharp phase transformation from the ferroelectric to the paraelectric phase.
关键词： dielectrical properties,Barium titanate,ceramics
更新于2025-09-09 09:28:46
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Effects of sintering temperature on microstructure and magnetic properties of NiCuZn ferrites for NFC application
摘要： Permeability and Q-factor are important factors for the near-field communication (NFC) techniques. To obtain great performance at high frequency (~13.56 MHz), Ni0.368Cu0.2Zn0.432Fe2O3 ferrite ceramics doped with Co2O3 were synthesized by the solid-state reaction method. XRD shows a pure spinel phase of NiCuZn ferrite ceramic can be formed without other phase while a sintering temperature varying from 1000 ℃ to 1100 ℃. Results indicate that an optimal volume of Co2O3 additive suppresses grain growth and lead to the formation of compact NiCuZn ferrite ceramics (the average grain size < 1 μm). We also find that grain size increase with enhancement of sintering temperatures. Meanwhile, fine dense grains of NiCuZn ferrite ceramics and relatively low sintering temperature are obviously enhancing Q-factor and improving permeability at 13.56 MHz. Finally, a Co2O3 substituted NiCuZn ferrite ceramics (x=0.2) with good permeability (~118 @13.56 MHz) and highly Q-factor (~50 @13.56 MHz) were obtained at the optimal sintering temperature ~1025 oC. The results reveal that the synthesized ferrite ceramics is an excellent material to be used in NFC systems.
关键词： NFC system,Co2O3,high frequency,NiCuZn ferrite ceramics
更新于2025-09-09 09:28:46
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Characterization of additively manufactured cellular alumina dielectric structures
摘要： Additive manufacturing (AM, also known as 3D printing) can produce novel three-dimensional structures using low-loss dielectric materials. This enables the construction of dielectrics with complex shapes that enable innovative microwave applications such as resonators, filters, and metamaterial lenses. This paper addresses the production and characterization of cellular structures of various designed densities created with a low loss ceramic material, alumina (aluminum oxide), via vat photopolymerization. The permittivity of these printed structures is variable over roughly an octave, with a range of relative permittivites from 1.78 to 3.60, controlled via part geometry.
关键词： electromagnetic metamaterials,dielectric materials,ceramics,printing,design for manufacture
更新于2025-09-09 09:28:46
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Synthesis of Transparent Nano-Ceramics under Ultra-High Pressure; 透明ナノセラミックスの超高圧合成;
摘要： Various transparent nano-ceramics have been synthesized using direct conversion from bulk glass starting materials under pressures higher than ～10 GPa and at high temperatures in Kawai-type Multi-anvil Apparatus (KMA). Rapid nucleation followed by slow crystal/grain growth is the key to synthesize such nano-ceramics at the ultra-high pressure regime. Thus synthesized novel ceramics have interesting features, such as higher hardness and lower thermal conductivity relative to those of the corresponding single crystals, in addition to their high optical transparencies, which may be useful for some scientific and industrial applications.
关键词： transparent nano-ceramics,KMA,ultra-high pressure,polycrystalline material,hardness
更新于2025-09-09 09:28:46