Yuchang Qing
材料科学技术（英）
Microwave absorbing properties of the carbonyl iron particles filled epoxy-silicone resin coatings showed visible degression when the coatings were heat treated at 300°C with different time. The complex permittivity and permeability of the coatings before and after heat treatment were measured. After heat treatment at 300°C, the real part of permittivity of the coatings increased with increasing treatment time and showed frequency dependence dielectric response. The complex permeability showed remarkable variation while the resonance frequency of the coatings heat treated at 300°C shifted from 7 to 12 GHz. The electromagnetic results indicated that microwave absorbing properties of the coatings showed more dependent on the complex permeability. The results showed that the difference of the electromagnetic and microwave absorbing properties before and after heat treatment was mainly attributed to the crystalline state transition of carbonyl iron particles.
关键词:
Microwave absorption
,
Dielectric properties
,
Magnetic properties
,
Heat treatment.
Shunhua Wu Xuesong Wei Xiaoyong Wang Hongxing Yang Shunqi Gao
材料科学技术（英）
High performance X8R dielectric ceramics were prepared by doping Bi2O3 to BaTiO3-based ceramics. The effect of small amounts (≤1.2 mol%) of Bi2O3 additive on the microstructure and dielectric properties of BaTiO3-based ceramics have been investigated. The Bi2O3, acting as a sintering additive, can effectively lower the sintering temperature of BaTiO3-based ceramics from 1300 to 1130°C. The bulk density of BaTiO3-based ceramics increased and reached the maximum value with increasing Bi2O3 content. The dielectric constant increased with increasing Bi2O3 until it reached the maximum value with 0.8 mol% Bi2O3 additive, and the dielectric loss decreased with increasing Bi2O3 content. Optimal dielectric properties of ε=2470, tanδ=0.011 and Δε/ε25≤±9% (-55-150°C) were obtained for the BaTiO3-based ceramics doped with 0.8 mol% Bi2O3 sintered at 1130°C for 6 h.
关键词:
BaTiO3-based ceramics
,
Bi2O3
,
Dielectric properties
,
X8R
Wang Li
材料科学技术（英）
CaCu3Ti4O12 ceramics substituted by Mg for Ca were prepared by the solid state reaction method. The crystal structures, microstructures, and dielectric properties of the Ca1-xMgxCu3Ti4O12 ceramics were investigated. At lower doping concentrations, the substitution of Mg for Ca caused a decreased lattice constant, while at higher doping concentrations, some of the Mg dopants started to replace Ti and resulted in an increased lattice constant, and some could also replace Cu due to the similar ion radius between Mg and Cu ions. Mg doping was found to promote the grain growth of Ca1-xMgxCu3Ti4O12 ceramics during sintering. Grain boundary resistance of the Ca1-xMgxCu3Ti4O12 ceramics was found to be increased by Mg doping. Enhanced dielectric properties was observed in the Ca1-xMgxCu3Ti4O12 ceramics with x=0.05 for the frequency range from 1 kHz to 20 kHz. For other doping concentrations, the dielectric losses of Ca1-xMgxCu3Ti4O12 ceramics were generally lowered.
关键词:
Electroceramics
,
Dielectric
,
CaCu3Ti4O12
,
Sintering
万正阳
,
孙彦胜
,
陈正威
,
宋桂林
低温物理学报
采用溶胶凝胶法制备BiFeO3和Bi0.95La0.05 Fe1-xCoxO3(x=0,0.05,0.1,0.15,0.2)样品.X衍射图谱表明所有样品的主衍射峰均与纯相BiFeO3相吻合且具有良好的晶体结构,La和Co共掺杂的结果导致BiFeO3的晶胞体积增大.SEM形貌分析可知,晶粒尺寸随着掺杂量的增加而逐渐减小,晶粒由原来的10um逐渐减小到1um,且其晶粒形状有不规则状逐渐呈现四方状.Bi0.95La0.05Fe1-xCoxO3样品介电常数和介电损耗随着掺杂量的增加先增大而后减小.当f=1kHz,Bi0.95 La0.05 FeO3的介电常数是BiFeO3的5.96倍.其介电特性是由偶极子的取向极化和空间电荷限制电流两种极化机制共同作用的结果.La3+和Co3+掺杂使BiFeO3晶胞体积增大、晶格结构发生扭曲形变,导致BiFeO3的Fe-O-Fe健的健角增大,改变Fe-O健健长,进一步提高了BiFeO3样品的铁磁性.
关键词:
铁磁电材料
,
介电特性
,
磁滞回线
