Alloys metallic interconnect

Besides the glass seal interfaces, interactions have also been reported at the interfaces of the metallic interconnect with electrical contact layers, which are inserted between the cathode and the interconnect to minimize interfacial electrical resistance and facilitate stack assembly. For example, perovskites that are typically used for cathodes and considered as potential contact materials have been reported to react with interconnect alloys. Reaction between manganites- and chromia-forming alloys lead to formation of a manganese-containing spinel interlayer that appears to help minimize the contact ASR [219,220], Sr in the perovskite conductive oxides can react with the chromia scale on alloys to form SrCr04 [219,221],... 

Newly developed alloys have improved properties in many aspects over traditional compositions for interconnect applications. The remaining issues that were discussed in the previous sections, however, require further materials modification and optimization for satisfactory durability and lifetime performance. One approach that has proven to be effective is surface modification of metallic interconnects by application of a protection layer to improve surface and electrical stability, to modify compatibility with adjacent components, and also to mitigate or prevent Cr volatility. It is particularly important on the cathode side due to the oxidizing environment and the susceptibility of SOFC cathodes to chromium poisoning. 

An important new application for MOCVD is the deposition of pure metal films for semiconductor integrated circuit applications. Important metals deposited by MOCVD include Al, Cu, CuAl alloys, and W films using precursors listed in Table I. It is expected that this application area for MOCVD will expand rapidly in the next few years as the demand increases for high-density metal interconnects for Si integrated circuit technology. High-purity Al metal films have also been grown by MOCVD. 

This chapter will provide an overview of oxidation and corrosion behavior of candidate oxidation-resistant alloys under SOFC operating conditions and discuss surface modifications for improved stability and performance of metallic interconnects. 

Prior to the introduction of Cu electroplating, the primary method used to form a multilevel structure of interconnections in integrated circuit applications was A1 and Al-alloy metallization.49 Localized porous-type anodization was developed in the 1970s to obtain planar interconnection metallization for multilevel large-scale integration (LSI) 26,46,50 For example, Schwartz and Platter showed that the subtractive etching for A1 interconnects could be substituted... 

The Ba0-Ca0-Al203-Si02 (BCAS) glass ceramic seal is often used for joining dissimilar materials, i.e. ceramic cells, metallic manifolds and metallic interconnects [2]. The ceramic seal should possess a satisfactory matching of the thermal expansion coefficient with the cells and the chosen alloy and it should also exhibit a long-term stability under the operation conditions. 

Chromium present in the alloy material of metallic interconnects is reported to have counter effects in the aging of SOFCs. On one hand Cr containing alloys lead to rapid degradation of electrical properties of SOFC due to Cr evaporation at the cathode side [22,36], but... 

Metal interconnects typically made of ferritic alloys have slightly higher thermal expansion coefficients than YSZ. A new alloy was produced so as to fit the thermal expansion of YSZ this is a Cr-based alloy, Cr5Fel Y2O3 [39]. Since this alloy is oxide dispersed and therefore quite hard, it is not easy to fabricate it into a desired shape. For this purpose, powder metallurgy process has been developed [40]. 

---