| Pulse forming line is an important device which can compress the power and shape the waveform of voltage. The key to get smaller pulse forming line is preparation an energy storage ceramic medium that has high dielectric constant and high dielectric breakdown strength. In this paper we get barium titanate powder coated by silica own “core shell” structure, study the effect of silica coating on the microstructures and energy storage properties of Ba Ti O3 ceramics, hypothes to search a new type of energy storage ceramic material that has high dielectric constant and high dielectric breakdown strength contrbute to the development of pulse forming line.Firstly this paper studies the fabrication of core-shell structure for barium titanate powder. Then discusse the effect of core-shell structure powder on the electric properties of ceramics by contrast test. Results are illustration(1) We get core-shell structure powder by silica coating on barium titanate surface as by St?ber method. The research show that: The silica coating on barium titanate surface get core-shell structure powder and grain size of barium titanate can be difference. The thickness of shell can be controled by adding differenct content of TEOS in the case of p H and solution concentration being constant.(2) The study of energy storage medium ceramic sintering by “core shell” structure powder with different content silica coating on surface of barium titanate with 100 nm grain size noticed that: The dielectric breakdown strength can be 157 k V/cm and the energy storage is 0.837 J/cm3 for ceramic sintering by barium titanate powder coated 3wt% silica, at the same time the dielectric constant is 1600 measure at room temperature 1 k Hz, are better than pure barium titanate ceramic.Most of the ceramics own large leakage so that the dielectric breakdown strength do not present certain regularity.Also we choose barium titanate powder the grain size is 300 nm as core and different content of silica as shell,get the “core shell” structure powder.The result show that the grain size stay at 300 nm do notgrow up for the effect of silica shell,the temperature depend dielectric constant has been improved which can satisfy the performance index of X8 R,the more content of silica for “core shell” structure powders the higher of dielectric breakdown strength for ceramics.Most important the ceramic sintering by 2wt% silica “core shell” structure powder has an excellent properties such as the dielectric constant is 2416 and dielectric loss is about 0.01 measured at room temperature 1 k Hz, the temperature depend dielectric constant can satisfy the performance index of X8 R, the dielectric breakdown strength improved to 201 k V/cm,the energy storage is 1.2 J/cm3.(3) Also we study the relationship between structure and properties of Nb2O5-doped ceramics which is sintering by “core shell” structure powder mixed trace Nb2O5 and investigate the chang of these ceramics' s properties under different sintering and anneling temperature.The result show that sintering temperature has no effect on properties of ceramics sintering by “core shell” structure powder,which is conducive to the use of base metal electrode and reduce the cost of material production in the miniaturization process. The dielectric constant is 57000 with 0.08 dielectric loss at the effect of oxygen vacancy for ceramic sintering by 2wt% silica “core shell” structure powder mixed trace niobium pentoxide sintering at 1300? N2 atmosphere. Thermal annealing the ceramic samps at 800? for 8 h,the performance of electric properties is better than the original ceramic such as dielectric constant can be 16500 with 0.04 dielectric loss,the break down strength attain 37.7 k V/cm.However change the annealing temperature to 950? for 12 h, dielectric constant is 6400 with 0.03 dielectric loss, break down strength improved to 135 k V/cm with 0.638 J/cm3 energy storage, which is an excellent ceramic for pulse forming line. |
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