Exotic Manganese Dioxide Structures in Niobium Oxides Capacitors

Abstract

The production of a Tantalum solid electrolytic capacitor requires the impregnation of MnO₂ by pyrolysis in one of the several manufacturing steps. It has been reported that niobium oxides are a good alternative, presenting potentially better dielectric properties and a better cost effectiveness. Thus, it is important to study the conditions and the effect of the MnO₂ impregnation on niobium oxide in order to understand and optimize the parameters of this process. The morphology and microstructure of the anode is one of the most important aspects that interfere with the dielectric properties of the capacitor. In this work, it is presented a study of the morphology and microstructure of different niobium oxide anodes after electrochemical oxidation (NbO/Nb₂O₅ core-shell grain structure), and after MnO₂ impregnation with different pyrolysis temperatures. This impregnation is made by dipping the anodes, with the NbO/Nb₂O₅ core-shell structure, in a slurry of Mn(NO₃)₂. Heating this slurry while the anode is dipped, will lead to a pyrolysis reaction where the liberation of NO₂ occurs as a gas, and where the product MnO₂ solidifies around the grains.