Tantalum capacitor electrodes

The range of electrical conductivity of various materials is illustrated in Figure 18. Many of the semiconductive or conductive polymer membrane applications involve optoelectronic applications discussed in the next section. Other applications where these polymer membranes are utilized include antistatic coatings, tantalum capacitor electrodes. 

Satoh, M., et al. 1995. Characterization of a tantalum capacitor fabricated with a conducting polypyrrole as a counter electrode. Synth Met 71 2259. 

One of the most widespread technical applications of PEDT is its use as a counterelectrode in solid aluminum, tantalum, and niobium electrolytic capacitors. As early as 1988, the application of PEDT as polymeric counter electrode in a tantalum capacitor was described in a patent application [62]. Since then, more than 100 patent applications have been filed which claim the use of PEDT in various capacitor configurations, and most major capacitor manufacturers today produce polymer capacitors. ... 

FIGURE 10.11 Process of forming the PEDT counter electrode in tantalum capacitors. 

Seff-heaUng processes in tantalum capacitors with Mn02 and polypyrrole electrodes occurs during the local breakdown at defect regions and it can regenerate capacitor structure. These events usually result in leakage current and noise decreasing in affected samples. 

Now the chemical company is marketing the polythiophene under the trade name Baytron. The material could also be used to make plastics paintable by adding the conductive agent first, or in the electrodes of small, high-performance tantalum capacitors found in telecommunications, computer, and automotive products. 

Aluminum foil capacitors occupy an important position in circuit applications due to their unsurpassed volumetric efficiency of capacitance and low cost per unit of capacitance.328 Together with tantalum electrolytic capacitors, they are leaders in the electronic discrete parts market. Large capacitance is provided by the presence of extremely thin oxide layers on anodes and cathodes, and high surface areas of electrodes could be achieved by chemical or electrochemical tunnel etching of aluminum foils. The capacitance of etched eluminum can exceed that of unetched metal by as much as a factor of 50.328... 

The use of tantalum to make miniaturized electrolytic capacitors that store electric charges in devices such as cell phones and computers is becoming increasingly popular. Powdered tantalum is used in the process of sintering to form malleable bars and plates as well as special electrodes for the electronics industry. 

To prepare these capacitors, the surface of an aluminum or tantalum electrode was roughened by etching or metal powder can be sintered to obtain a high-surface-area electrode with high capacitance. A thin film of metal oxide, which would serve as a dielectric, can be applied to the electrode by anodization. A counter electrode was ultimately applied to complete the capacitor. In the preparation of conventional capacitors, this last step was performed by multiple impregnations with manganese nitrate solution and P50 olysis was applied to form electrically conductive manganese dioxide. 

Fig. 39.1. (a) Schematic representation of a microsupercapacitor copper current collector (a), HUP pure ionic membrane (b), composite HUP/C electrodes (c), and plastic encapsulation (d). Diameter (D) is 10 mm and thickness (t) is 2 mm. The capacity is 1F. (b) Comparison of specific energy storage capability (capacitance x voltage per unit volume — CV/V ) vs. capacitance (C). Pp, polypropylene film capacitors Pe, polyethylene film capacitors Ta, tantalum electrolytic capacitors Al, aluminium electrolyte capacitors H2SO4/C, liquid-solid supercapacitors HUP/C, all-solid supercapacitor (with permission, American Institute of Physics). 

Further miniaturization of chip capacitors with thinning the dielectric layer and electrode laydown is also effective for the production cost. By incorporating thinner dielectric layers with nickel compatible dielectrics and nickel electrode, large capacitance MLCs comparable to tantalum electrolytic capacitors have been developed. To reduce the dielectric thickness less than few micrometers, further development of ultrafine grain BaTiOs is indispensable. 

In practice, the two major types of electrolytic capacitors are (1) aluminum electrolytic capacitors and (2) tantalum electrolytic capacitors. Aluminum electrolytic capacitors are fabricated from two conducting aluminum foils, one of which is coated with an insulating oxide layer and a paper spacer soaked in electrolyte. The foil insulated by the oxide layer is the anode while the liquid electrolyte and the second foil act as the cathode. Tantalum electrolytic capacitors are subdivided into wet and dry types based on whether their counter electrodes are served by sulfuric acid or a manganese dioxide film. Dry tantalum electrolytic capacitors possess a greater capacitance-to-volume ratio relative to aluminum counterparts and are utilized in computer and... 

Although not commercialized, A1 electrolytic capacitors using CPs as the counter-electrode (rather than the electrolyte, as in the Matsushita capacitor) have been well studied. One such capacitor was studied by Li et al. [999]. Satoh et al. [1000] investigated the use of a P(Py) "composite" counter electrode in a tantalum electrolytic capacitor. Capacitance/loss factor and impedance curves are shown for this capacitor in Figs. 23-21a.b. 

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