As a leading tantalum & niobium producer, H.C. Starck acquired a deep knowledge about the interaction of microstructure and properties for capacitor applications. This paper gives an overview about three current topics. Production of tantalum pellets with high surface area shows that the wire that can be embedded in or welded to the pellet shows an increasing tendency for embrittlement. In the past wire embrittlement has been observed when high sinter temperatures have been used. The cause for this was oxygen that has been diffused from the pellet into the wire. High surface area pellets are sintered at much lower temperatures, where oxygen migration is low and can not be the reason for embrittlement. It will be shown, that wires of high surface area pellets are embrittled by hydrogen that is created during passivation from the moisture in air. The possibilities to improve wire embrittlement stability will be reported.
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