Tantalum Electrolytic Capacitors With ¦Â Dioxide Manganese Cathodes Study

Tantalum capacitor is a kind of electronic product which has beenwidely applied in communication, compute, radar, missile and aviationwith high reliability, low leaky current and stable performance. Thecathode material of Tantalum capacitor isβ-MnO₂. In this research, thechemical precipitation-crystal phase transformation method was utilizedto prepareβ-MnO₂ satisfied the demand on chemical purity, particle size,morphology and crystal configuration. The basic conception of theresearch is using chemical precipitation to prepare MnCO₃ with theparticle size and morphology in control, which will be transformed intoβ-MnO₂ with the purity above 99ï¼…through heat decomposition,acid-washing and crystal phase transformation. The research consists ofthree key processes: the preparation of ultra-fine dispersed MnCO₃, theheat decomposition in which MnCO₃ was transformed into MnO₂, andthe crystal phase transformation of MnO₂.In chemical precipitation of ultra-fine dispersed MnCO₃, thedispersed MnCO₃ particles with the size between 2～3.5μm and themorphology of sphere were prepared through the control of charging style,time and temperature. The optimum technological conditions ofpreparation were determined.The temperature range of heat decomposition for MnCO₃ wasdetermined according to the thermodynamic analysis, the diagram ofdecomposition pressure lgpo₂ and 1/T for MnO₂, the DSC-TGA analysisand the isotonic decomposition curve of MnO₂, which reveals that theproduction of MnO₂ will greatly increase in the presence of oxygen withhigh concentration. The results shows that the production of MnO₂increases above 82ï¼…with the oxygen concentration as 50ï¼…and the heatdecomposition at 400℃for 2 hours.The crystal phase transformation of MnO₂ is the most significantprocess in this work. According to the DSC-TGA analysis and X-raydiffraction analysis of MnO₂, the temperature range of the crystal phasetransformation was determined as 300～450℃. On the basic of heat treating at different time and temperature, the optimum technologicalcondition of crystal phase transformation was determined as heat treatingfor 5～10 hours at 450℃.