| Barium titanate materials have a wide range of applications in electronics industry because of the high dielectric constant and high breakdown strength. Barium titanate based super capacitors have the properties of solid state and high pressure resistance. However, the dielectric loss of barium titanate based capacitors is comparatively high in low frequency area and the self-discharge phenomenon is relatively severe, these disadvantages limit the application and development of barium titanate based capacitor. So the direction of the research should focus on reducing the dielectric loss of the dielectric material, and then obtain the super capacitors which possess high dielectric properties and high capacity performance in the low frequency area. In this paper, a layer of oxide was introduced around the barium titanate, the barium titanate composite film materials which have excellent performance was prepared. Then the low-frequency dielectric preformance of composite film material was explored, the relationship between the structure and performance was analyzed. Then, the super capacitor was assembled, the capacity performance of low frequency was discussed and the stability of the low frequency test was explored. The main contents and results are as follows:1. Adopted graphite as electrode material, a layer of oxide (B2O3 monolayer film, BiO2-SiO2 composite films) was introduced between the graphite electrode and barium titanate thin film. Discussed the optimal mixing proportion of SiO2 and B2O3 was 3:1. B2O3-SiO2 composite film was successfully achieved.900℃ was the best processing temperature of B2O3-SiO2/BaTiO3 thin films of the different temperature treatment, and the dielectric layer showed excellent dielectric properties at 900℃, the dielectric constant was 1108, dielectric loss was 0.4345 under 1Hz. Through the comparison of different heating rate could found that heating rate of 2℃/min could promote the melting of B2O3-SiO2 and formed a homogenous layer, then the the performance of the dielectric layer was promoted. In addition, the B2O3-SiO2/ BaTiO3 film capacitor was prepared by laminated method.2. Adopted the cheap aluminium as electrode material, a layer of thermal oxidation film between the barium titanate and aluminum electrode was generated by the method of heat-treatment in air, the electrodes and the insulating layer could be integrated. The formation of thermal oxidation film and aluminum electrode existence state were influenced by different heat treatment system, thus increase the effective contact area of electrode and aluminum oxide layer and the content of aluminum. The optimum conditions of heat treatment was 10℃/min.120 min, the dielectric constant was 3.84×104 at 500 mHz and the dielectric constant increased obviously in the low frequency, dielectric loss was 0.2801, the largest capacitance of capacito was 2.92 uF. Eventually the dielectric loss was reduced and the capacity of Al/Al2O3/ BaTiO3 film capacitor was improved.3. Adopted triethanolamine as the treatment fluid, the aluminum treated with triethanolamine before pulled the barium titanate will form chemical conversion coatings (AIO(OH)), eventually the alumina content of the thin film would improved. The structure and morphology of alumina were changed by different oxidation treatment system. At last the optimal oxidation conditions were determined:the oxidation rate was 10℃/min. oxidation time was 30 min. The existence of alumina could promote the dielectric and capacity performance of barium titanate, the dielectric constant was 4.96×104 and the capacitance reached 3.95 μF under 500 mHz. And then 100 V.200 V.300 V high voltage charging and discharging, it was concluded that the capacitor had a high voltage resistance and the capacity density of the capacitor was calculated. The electrochemical properties of alumina and barium titanate were explored through the equivalent circuit fitting analysis, and the combination of the alumina and barium titanate was verified, the existence of alumina was proved. What’s more, The performance of the capacitors which were treated by triethanolamine or not was compared, the capacitor treated by triethanolamine had more excellent dielectric performance, and the triethanolamine played an important role in the preparation of Al/Al2O3/BaTiO3 film capacitor.4. The low frequency stability of the Al/Al2O3/BaTiO3 thin film capacitor was discussed by the new test method (EIS fixed frequency test), the influence of amplitude, test cycle and frequency to the stability of capacitor was discussed. The results concluded that the amplitude, test cycle and frequency had certain influence on the stability of capacitors, and the largest influence was come from the frequency. What’s more, the equivalent formula model between test cycle and frequency was established. The feasibility for shorten test time and improve the efficiency of the EIS test was confirmed. |
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