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991.
Hao Chen Jie Xing Jingwen Xi Tao Pu Hong Liu Jianguo Zhu 《Journal of the American Ceramic Society》2021,104(12):6266-6276
The Ag-Pd internal electrode of multilayer piezoelectric ceramics needs to be sintered below 1000°C, and lead wires and components need to be welded with lead-free solder at 260°C. PNN–PMW–PZT–xSr piezoelectric ceramics with high Curie temperature (Tc > 260°C) were synthesized at a low sintering temperature (960°C) to meet the requirements of multilayer piezoelectric devices. The relationship between structures (phase, domain, and microstructures) and electrical properties (piezo/ferroelectric properties, and dielectric relaxation) in the Sr2+ substituted ceramics was investigated. Rietveld refinement and Raman spectra show that Sr2+ substitution can cause the phase change and increase the force constant of [BO6] octahedron. The piezoelectric response increases with increasing the content of the tetragonal phase (CTP) in the rhombohedral-tetragonal (R-T) coexisted ceramics. The ceramics with 0.6 mol% Sr2+ substitution have minimum activation energy for domain wall movement (Ea) of 0.0362 eV which favors the formation of nanometer-sized domains, and possess excellent electrical properties (d33 = 623 pC/N, d33* =783 pm/V, Tc =295°C). The higher the CTP, the lower the Ea. The lower Ea favors the rotation of polarization direction and extension, and is beneficial to the generation of the nanometer-size domains, resulting in high piezoelectric properties. 相似文献
992.
The most important polymer film used in commercial capacitors is biaxially oriented polypropylene (BOPP), which could be produced by sequentially or simultaneously biaxial orientation after the melt-extrusion. In order to disclose the influence of the stretching technique on the properties of films, the BOPP films with varied thickness were fabricated by sequential and simultaneous orientation, respectively. Compared to the sequentially biaxially stretched films, the crystal grains in the simultaneously biaxially stretched films are more isotropically dispersed. As temperature increases, all the BOPP films exhibit similar dielectric constant, and the simultaneous films have much lower dielectric loss thanks to the finer blended crystalline and amorphous phases. When the film thickness is smaller than 5 μm, the breakdown field strength, energy density and discharging time of the simultaneous films can be increased by at least 10% comparing to the sequential ones, which is very important for reducing the volume of the film capacitors. All the results suggest the simultaneously biaxial orientation mode shows significant advantages in producing thin BOPP films with better mechanical and electrical properties. 相似文献
993.
Junqi Chen Weishuang Fang Yifan Zhai Feihu Li Ying Tang Jie Li Huanhuan Guo Liang Fang 《Journal of the European Ceramic Society》2021,41(8):4473-4477
Orthorhombic-structured CaIn2O4 ceramics with a space group Pca21 were synthesized via a solid-state reaction method. A high relative density (95.6 %) and excellent microwave dielectric properties (εr ~11.28, Qf = 74,200 GHz, τf ~ ?4.6 ppm/°C) were obtained when the ceramics were sintered at 1375 °C for 6 h. The dielectric properties were investigated on the basis of the Phillips–Van Vechten–Levine chemical bond theory. Results indicated that the dielectric properties were mainly determined by the InO bonds in the CaIn2O4 ceramics. These bonds contributed more (74.65 %) to the dielectric constant than the CaO bonds (25.35 %). Furthermore, the intrinsic dielectric properties of the CaIn2O4 ceramics were investigated via infrared reflectivity spectroscopy. The extrapolated microwave dielectric properties were εr ~10.12 and Qf = 112,200 GHz. Results indicated that ion polarization is the main contributor to the dielectric constant in microwave frequency ranges. 相似文献
994.
Bingcheng Luo Xiaohui Wang Enke Tian Hongzhou Song Qiancheng Zhao Ziming Cai Wei Feng Longtu Li 《Journal of the European Ceramic Society》2018,38(4):1562-1568
Fe doped BaTiO3 ceramics with giant permittivity and low dielectric loss were synthesized in N2/H2 atmosphere started with BaTiO3 powders and iron powders. XRD analysis exhibited the tetragonal-pseudocubic phase transition when the Fe content is 3 mol%. XPS spectra confirmed the iron oxides with mixed-valence structure of Fe2+/Fe3+, while Ti-ions maintain Ti4+3d0 states without any oxidization-reduction. For the case of ceramics with 5 mol% Fe, the dielectric constant was 66,650 at 1000 Hz at room temperature, 19 times higher than that of pure BaTiO3 ceramics, while the dielectric loss tangent was 0.13. Comparison with other giant-permittivity materials demonstrated the superior potential of present ceramics. First-principles calculations investigated the interfacial interaction of Fe-[TiO2] interface and Fe-[BaO] interface. Giant dielectric constant was induced by the interfacial polarization between insulating ferroelectrics and semiconducting iron oxides with mixed-valence states, as well as the contribution from the generated electron hopping conduction. 相似文献
995.
The (K1-xNax)2Mo2O7 (0.0?≤?x?≤?0.3) ceramics with ultra-low sintering temperatures were prepared by a modified solid-state reaction method. Polyvinyl ethanol (PVA) binder was replaced by ethanol and isostatic pressing technology was used, which improved the density of the ceramics effectively and avoided the side effect of the residual PVA. When x?≤?0.3, the (K1-xNax)2Mo2O7 ceramics are with a triclinic phase and all components can be sintered well at 450?°C. The substitution of Na+ at the K-site modified the dielectric properties of K2Mo2O7 ceramic and in particular increased the Q?×?f value. Among all the components, the (K0.8Na0.2)2Mo2O7 ceramic exhibited the best microwave dielectric properties with a permittivity of 8.7, a Q?×?f value of 50 300?GHz and a temperature coefficient of ?64?ppm/°C. The (K1-xNax)2Mo2O7 (0.0?≤?x?≤?0.3) ceramics are very potential candidates for ultra-LTCC devices and the modified solid-state reaction method is an excellent substitution for the conventional solid-state method. 相似文献
996.
Xiao-Qiang Song Wen-Zhong Lu Xiao-Chuan Wang Xiao-Hong Wang Gui-Fen Fan Raz Muhammad Wen Lei 《Journal of the European Ceramic Society》2018,38(4):1529-1534
BaAl2?2x(ZnSi)xSi2O8 (x = 0.2–1.0) ceramics were prepared using the conventional solid-state reaction method. The sintering behaviour, phase composition and microwave dielectric properties of the prepared compositions were then investigated. All compositions showed a single phase except for x = 0.8. By substituting (Zn0.5Si0.5)3+ for Al3+ ions, the optimal sintering temperatures of the compositions decreased from 1475 °C (x = 0) to 1000 °C (x = 0.8), which then slightly increased to 1100 °C (x = 1.0). Moreover, the phase stability of BaAl2Si2O8 was improved. A novel BaZnSi3O8 microwave dielectric ceramic was obtained at the sintering temperature of 1100 °C. This ceramic possesses good microwave dielectric properties with εr = 6.60, Q × f = 52401 GHz (at 15.4 GHz) and τf = ?24.5 ppm/°C. 相似文献
997.
Emilio Pradal-Velázquez Fan Yang Derek C. Sinclair 《Journal of the American Ceramic Society》2020,103(12):6801-6810
The compositional limits of a previously reported (J. Am. Ceram. Soc., 61, 5-8. (1978)) but relatively unstudied sodium-bismuth titanate pyrochlore solid solution are revised and their electrical properties presented. The pyrochlore solid solution we report forms via a different mechanism to that originally reported and occurs in a different location within the Na2O-Bi2O3-TiO2 ternary system. In both cases, relatively large amounts of vacancies are required on the A-sites and on the oxygen sites, similar to that reported for undoped ‘Bi2Ti2O7’ pyrochlore. In contrast to ‘Bi2Ti2O7’, this ternary pyrochlore solid solution can be prepared and ceramics sintered using conventional solid-state methods; however, the processing requires several challenges to be overcome to obtain dense ceramics. This cubic pyrochlore series has low electrical conductivity (and does not exhibit any evidence of oxide-ion conduction) and exhibits relaxor ferroelectric behavior with a broad permittivity maximum of ~100 near room temperature. Variable temperature neutron diffraction data do not provide any conclusive evidence for a phase transition in the pyrochlore solid solution between ~4 and 873 K. 相似文献
998.
Chung-Ya Tsao Wei-Hsing Tuan Kuei-Chih Feng 《International Journal of Applied Ceramic Technology》2019,16(5):2094-2100
In this study, relationships between the processing, microstructure, and properties of barium niobate (Ba5Nb4O15) are investigated. The milling of a Ba5Nb4O15 powder in water is effective with respect to size reduction. However, after milling in water, BaCO3 is formed within the slurry. With the increase in the amount of BaCO3 formed, the aspect ratio of the elongated Ba5Nb4O15 grains increases. The formation of the elongated Ba5Nb4O15 grains prohibits the densification. Hence, the microwave dielectric properties, including permittivity and quality factor, are poor because of the low density. In addition, milling in ethanol is carried out for comparison: A lower amount of BaCO3 is formed after milling in ethanol; the extent of anisotropic grain growth is thus reduced. 相似文献
999.
Xianjie Zhou Kangguo Wang Sang Hu Xiaowen Luan Sen He Xi Wang Shicheng Zhou Xiuli Chen Huanfu Zhou 《Ceramics International》2021,47(6):7783-7789
A novel La2MgGeO6 ceramic was synthesized through a solid-state reaction process within a sintering temperature range of 1450–1550 °C. By a combination of X-ray diffraction and Rietveld refinement analyses, the ceramics were found to have a pure hexagonal phase structure belonging to space group R3/146. The scanning electron microscopy images revealed that the ceramic grains were closely connected. The effects of internal (lattice energy, valence bond, and fraction packing) and external factors (density) on the microwave properties of ceramics were also studied. The ceramic exhibited excellent microwave dielectric performances, with a relative permittivity (?r) of 21.2, a quality factor (Q × f) of 52 360 GHz, and a temperature coefficient of resonant frequency (τf) of ?44.2 ppm/°C, when sintered at 1500 °C for 4 h. The τf value of the La2MgGeO6 ceramic doped with CaTiO3 could be adjusted to zero. Particularly, 0.2La2MgGeO6-0.8CaTiO3 ceramics have good microwave dielectric properties with τf = +2.1 ppm/°C, Q × f = 15 610 GHz, and ?r = 40.3. 相似文献
1000.
Shruti Mendiratta Cheng-Hua Lee Muhammad Usman Kuang-Lieh Lu 《Science and Technology of Advanced Materials》2015,16(5)
Metal–organic frameworks (MOFs) have been intensively studied over the past decade because they represent a new category of hybrid inorganic–organic materials with extensive surface areas, ultrahigh porosity, along with the extraordinary tailorability of structure, shape and dimensions. In this highlight, we summarize the current state of MOF research and report on structure–property relationships for nonlinear optical (NLO) and dielectric applications. We focus on the design principles and structural elements needed to develop potential NLO and low dielectric (low-κ) MOFs with an emphasis on enhancing material performance. In addition, we highlight experimental evidence for the design of devices for low-dielectric applications. These results motivate us to develop better low-dielectric and NLO materials and to perform in-depth studies related to deposition techniques, patterning and the mechanical performance of these materials in the future. 相似文献