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采用改性共沉淀法合成了La9.33Si6O26-10wt%Zr0.86Y0.14O1.92两相共存的氧离子导电复合材料,利用X射线衍射、扫描电子显微镜、交流阻抗技术分别表征了材料的相组成、微观组织和离子导电性.结果表明,复合材料粉体平均晶粒尺寸为35 nm,烧结块体的平均颗粒尺寸为500 nm;在300~700℃温度范围内,复合材料的导电率均高于La9.33Si6O26或Zr0.86Y0.14O1.92单相材料,且700℃时比La9.33Si6O26高出1个数量级.结合交流阻抗谱及电模量谱对复合材料的导电机理进行了分析讨论. 相似文献
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以柠檬酸做络合剂,硝酸盐做氧化剂,采用柠檬酸-硝酸盐自燃烧法一步合成了具有扭曲菱方钙钛矿结构的BiFeO3粉体.利用X射线衍射(XRD)、差热-热重(DTA -TG)等技术分析了所得BiFeO3粉体,并研究了粉体烧结后BiFeO3陶瓷的相结构和电性能.结果表明,柠檬酸盐溶胶-凝胶法制备的前驱体具有自燃烧特性,自燃烧后B... 相似文献
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以溶胶凝胶法制备负热膨胀材料ZrW2O8粉体并与固相法制备的粉体相比较.对其前驱体进行热重-差热分析(TG-DSC)、以X射线粉末衍射(XRD)、透射电镜(TEM)、扫描电子显微镜(SEM)分别对粉体进行物相分析和形貌观测.结果表明溶胶凝胶法比固相法合成温度低,于610℃合成单一立方结构ZrW2O8粉体,并且粉体颗粒比固相法小,为100nm;ZrW2O8粉体有很好的负热膨胀特性,以高温X射线衍射分析,在室温约500℃范围内,溶胶凝胶法制备的粉体的热膨胀系数为-5.93×10-6/K;比固相法(-6.31×10-6/K)的略低. 相似文献
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用熔盐法和固相法合成SrBi4Ti4O15粉体,对其微观形貌进行了对比.熔盐法合成的粉体片状结构明显,合成温度低,比固相合成合成温度低50℃,一定程度上避免了Bi2O3的挥发.热压烧结的SrBi4Ti4O15陶瓷在(001)面取向非常明显,其压电性能也得到提高. 相似文献
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以溶胶凝胶法制备负热膨胀材料ZrW2O8粉体并与固相法制备的粉体相比较.对其前驱体进行热重-差热分析(TG-DSC)、以X射线粉末衍射(XRD)、透射电镜(TEM)、扫描电子显微镜(SEM)分别对粉体进行物相分析和形貌观测.结果表明溶胶凝胶法比固相法合成温度低,于610℃合成单一立方结构ZrW2O8粉体,并且粉体颗粒比固相法小,为100nm;ZrW2O8粉体有很好的负热膨胀特性,以高温X射线衍射分析,在室温约500℃范围内,溶胶凝胶法制备的粉体的热膨胀系数为-5.93×10-6/K;比固相法(-6.31×10-6/K)的略低. 相似文献
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采用以尿素为燃料的低温燃烧法一步合成了电解质粉末Ce0.8Gd0.2O1.9(GDC),通过XRD、TGDSC、BET、FESEM等手段对合成粉体进行了物相测定、热分析、比表面积测定和形貌观察,并考察了粉体的烧结性能。结果表明,尿素-硝酸盐干凝胶自蔓延燃烧点火温度约为279.0℃。通过工艺参数的有效设计,经过低温燃烧过程即可直接得到立方萤石结构的纯相GDC粉体,该粉体为粒径在20~60nm的类球形颗粒,粒子间虽有微弱的软团聚,却具有较高的烧结活性,在1 300℃仅需烧结2h即可达到95.2%的相对密度。该温度比固相法制备该粉体的烧结温度至少降低300℃。 相似文献
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La0.67Ca0.33MnO3 (LCMO)/La0.67Sr0.33CoO3 (LSCO)/LCMO trilayer films are fabricated on single-crystal substrates NdGaO3 (110) and the interlayer coupling are investigated. Compared with LCMO single layer, sandwiches showed the enhanced metal-insulator transition temperature of LCMO layers. The magnetoresistance is dependent on spacer thickness and the peak value dramatically decreases when LSCO layer is thick enough because of shorting by the LSCO layer. The magnetic coercivity HC shows a nonmonotonic behavior with changing spacer layer thickness and the waist-like hysteresis indicates that there is an indirect exchange coupling between the top and bottom LCMO layers across the spacer layer. 相似文献
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Choon-W. Nahm 《Materials Letters》2011,65(9):1299-1301
The varistor properties of the ZnO-Pr6O11-CoO-Cr2O3-Y2O3-In2O3 ceramics were investigated for different concentrations of In2O3. The increase of In2O3 concentration slightly increased the sintered density (5.60-5.63 g/cm3) and slightly decreased the average grain size (3.4-2.9 μm). The breakdown field increased from 6023 to 14822 V/cm with increasing concentration of In2O3. The nonlinear coefficient increased from 17.6 to 44.6 for up to 0.005 mol%, whereas the further doping caused it to decrease to 36.8. In2O3 acted as an acceptor due to the donor concentration, which decreases in the range of 1.02 × 1017 to 0.24 × 1017/cm3 with increasing concentration of In2O3. 相似文献
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Transparent glasses in the system (100−x)Li2B4O7–x(SrO---Bi2O3---Nb2O5) (10≤x≤60) (in molar ratio) were fabricated by a conventional melt-quenching technique. Amorphous and glassy characteristics of the as-quenched samples were established via X-ray powder diffraction (XRD) and differential thermal analyses (DTA) respectively. Glass–ceramics embedded with strontium bismuth niobate, SrBi2Nb2O9 (SBN) nanocrystals were produced by heat-treating the as-quenched glasses at temperatures higher than 500 °C. Perovskite SBN phase formation through an intermediate fluorite phase in the glass matrix was confirmed by XRD and transmission electron microscopy (TEM). Infrared and Raman spectroscopic studies corroborate the observation of fluorite phase formation. The dielectric constant (r) and the loss factor (D) for the lithium borate, Li2B4O7 (LBO) glass comprising randomly oriented SBN nanocrystals were determined and compared with those predicted based on the various dielectric mixture rule formalism. The dielectric constant was found to increase with increasing SBN content in LBO glass matrix. 相似文献
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Epitaxial YBa2Cu3O7/La0.7Ca0.3MnO3 (YBCO/LCMO) bi-layers and La0.7Ca0.3MnO3/YBa2Cu3O7 (LCMO/YBCO) bi-layers were grown on (001)LaAlO3 by pulsed laser deposition, and their microstructures were compared by transmission electron microscopy investigation. In the YBCO(100 nm)/LCMO(150 nm) bi-layers, the LCMO layer consists of columnar grains of ~ 17 nm in diameter and contains mixed orientation domains of [100]c, [010]c and [001]c. The YBCO layer is totally c-axis oriented and the YBCO lattices are tilted − 2.5° to + 2.5° as they grew on the rough surfaces of LCMO columnar grains. For the LCMO(140 nm)/YBCO(140 nm) bi-layers, the LCMO/YBCO interface is sharp and flat. The initial 12-nm thickness of the YBCO layer is composed of c-axis oriented domains, and the upper part of YBCO layer is [100] oriented. The LCMO layer was predominantly [001]c oriented while [100]c-oriented domains were occasionally observed. 相似文献
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Hollandite-type compounds, Rb2Cr8O16, K2Cr2V6O16 and K2V8O16, were synthesized under high P-T conditions up to 1200°C and 7GPa. The structural refinement using a single crystal of Rb2Cr8O16 confirms that the structure is similar to that of K2Cr8O16. Magnetic measurements indicate that Rb2Cr8O16 is ferromagnetic below 295K, K2Cr2V6O16 paramagnetic down to 77K and K2V8O16 has susceptibility anomaly at 175K. These compounds are all semiconductive and show discontinuities in temperature-resistivity curves at points corresponding to magnetic anomalies. 相似文献
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A systematic study was performed with mixtures consisting of N2, CH4, C2H6 and C3H8, to investigate experimentally phase equilibria and caloric properties and to test the accuracy of thermodynamic correlations. The first part of this Paper reports results of T---p---x---y measurements on ternary systems in the range 20 < p < 120 bar and 140 < T < 220 K. The results are compared with data calculated by generalized equations of state. 相似文献
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G. R. Gurbanov 《Inorganic Materials》2012,48(9):888-890
Phase equilibria along the PbSbBiS4-Sb2S3 and PbSbBiS4-Bi2S3 joins of the PbS-Sb2S3-Bi2S3 system have been studied for the first time using differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements, and the phase diagrams of the joins have been mapped out. The joins are shown to be pseudobinary with limited series of terminal solid solutions. The solid solutions are p-type semiconductors. 相似文献
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We investigated the structural and superconducting properties ofc-axis oriented (YBa2Cu3O7)
nY
/(PrBa2Cu3O7)
npr
superlattices with thicknesses of the individual layers down to one unit cell (10nY1; 18>nPr 1). By transmission electron microscopy and X-ray diffraction we find an excellent structural quality of the samples, though the quantitative analysis shows the existence of defects. In superlattices with decoupled YBa2Cu3O7 layers of two unit cell thickness we find a highT
c
value of 75 K. We probed the flux line structure in the superlattices by measurements of the critical current density in magnetic fields. The experiments show that the flux-line dynamics is dominated by the movement of pancake vortices. 相似文献
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Xiaohua Sun Ying YangQiaoling Zhang Zhimeng LuoShuang Hou Caihua HuangJun Zou 《Materials Science and Engineering: B》2013,178(18):1244-1248
Bi1.5Zn0.5Nb0.5Ti1.5O7 (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba0.6Sr0.4TiO3 (BST) thin films on the Pt/Ti/SiO2/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces. 相似文献
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J.A. Luna-Lpez J. Portelles O. Raymond J.M. Siqueiros 《Materials Chemistry and Physics》2009,118(2-3):341-348
Sr0.3Ba0.7Nb2O6 (SBN) and La0.030Sr0.255Ba0.700Nb2O6 (LSBN) ceramic compounds have been prepared using the traditional ceramic method at two different calcination temperatures (900 and 1000 °C) and later sintered both at 1400 °C. A study of the effects of the calcination temperatures and La substitution on the morphological, compositional, and structural properties of SBN and LSBN is presented using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. From Rietveld refinement processes, the XRD patterns were interpreted to evaluate such effects in the structural parameters and the site occupation factors of the heavy metals and oxygen atoms. The effect of the incorporation of La resulted in a 0.25% cell contraction and turned out to be higher than the 0.08% dilation effect produced by the increase of calcination temperature. The La ion with similar effective ionic radius and higher electronegativity is incorporated into the structure occupying the A1 site just like the Sr ions in the SBN compound. Differences in the site occupation factors between the SBN and LSBN samples lead to substantial changes in the physical properties such as temperature of relative dielectric constant maximum, relative dielectric constant, and dielectric loss, correlated with the distortion and the relative orientation of the oxygen octahedra. 相似文献