Ferroelectric barium strontium titanate （BST） glass-ceramics doped with different content of La2O3 were prepared via the melt-quenching technique followed by controlled crystallization. The microstructures of crysta...Ferroelectric barium strontium titanate （BST） glass-ceramics doped with different content of La2O3 were prepared via the melt-quenching technique followed by controlled crystallization. The microstructures of crystallized samples were examined by X-ray diffraction and scanning electron microscopy. Dielectric properties were also investigated. The aliovalent substitution of Ba by La induced dispersion of semiconducting BaxSr1-xTi03 crystallites sealed in a glassy silicate matrix, which increased the εr and loss tangent values of the BST glass- ceramic. The experimental results indicate that aliovalent substitution is an effective method to process glass-ceramics with better dielectric properties.展开更多
To efficiently utilize the kaolin, an economical way of preparing cordierite ceramic with high performance for electric heater supports was put forward. In this study, sintering process, phase transformation, microstr...To efficiently utilize the kaolin, an economical way of preparing cordierite ceramic with high performance for electric heater supports was put forward. In this study, sintering process, phase transformation, microstructure evolutions were systematically studied by heating microscope, X-ray diffraction, scanning electronic microscope and thermal analysis. Properties（physical properties, electrical properties and coefficient of thermal expansion（CTE）） were tested for comprehensive performance evaluation. The results showed that the utilization of poor quality kaolin broadened the firing range of cordierite ceramic which was from 1 200 to 1 380 ℃. Microstructure becomes loose with increasing of the pore size, which had significant influence on bending strength and electrical properties. High content of K2 O in poor quality kaolin was the reason for liquid phase generation in sintering process, which further leads to microstructural changes. The cordierite ceramic sintered at 1 320 ℃ had the properties as follows： CTE of 1.98×10^（-6） ℃^（-1）（500 ℃）, bending strength of 90 MPa, apparent porosity of 15.1%, dielectric constant of 7.5（100 Hz）, and volume resistivity of 1.05×109 Ω·cm（100 Hz）. The comprehensive properties are very suitable for use as electric heater supports.展开更多
基金Financial supports from the National Natural Science Foundation of China (No. 50902082)the State Key Laboratory of Electrical Insulation and Power Equipment (EIPE11208) are gratefully acknowledged
文摘Ferroelectric barium strontium titanate （BST） glass-ceramics doped with different content of La2O3 were prepared via the melt-quenching technique followed by controlled crystallization. The microstructures of crystallized samples were examined by X-ray diffraction and scanning electron microscopy. Dielectric properties were also investigated. The aliovalent substitution of Ba by La induced dispersion of semiconducting BaxSr1-xTi03 crystallites sealed in a glassy silicate matrix, which increased the εr and loss tangent values of the BST glass- ceramic. The experimental results indicate that aliovalent substitution is an effective method to process glass-ceramics with better dielectric properties.
基金Funded by the Major State Basic Research Development Program of China(973 Program)(No.2010CB227105)
文摘To efficiently utilize the kaolin, an economical way of preparing cordierite ceramic with high performance for electric heater supports was put forward. In this study, sintering process, phase transformation, microstructure evolutions were systematically studied by heating microscope, X-ray diffraction, scanning electronic microscope and thermal analysis. Properties（physical properties, electrical properties and coefficient of thermal expansion（CTE）） were tested for comprehensive performance evaluation. The results showed that the utilization of poor quality kaolin broadened the firing range of cordierite ceramic which was from 1 200 to 1 380 ℃. Microstructure becomes loose with increasing of the pore size, which had significant influence on bending strength and electrical properties. High content of K2 O in poor quality kaolin was the reason for liquid phase generation in sintering process, which further leads to microstructural changes. The cordierite ceramic sintered at 1 320 ℃ had the properties as follows： CTE of 1.98×10^（-6） ℃^（-1）（500 ℃）, bending strength of 90 MPa, apparent porosity of 15.1%, dielectric constant of 7.5（100 Hz）, and volume resistivity of 1.05×109 Ω·cm（100 Hz）. The comprehensive properties are very suitable for use as electric heater supports.
