An Investigation of Electrical Contacts for Higher Manganese Silicide

Five metals with large work functions including Co, Ni, Cr, Ti, and Mo and two silicides including MnSi and TiSi 2 were examined to determine the best contact material for the thermoelectric material higher manganese silicide (HMS). Three-layer structures of HMS/contact/HMS were prepared in a sintering process. The contact resistance was measured versus temperature. The structures were subjected to x-ray diffraction and energy-dispersive x-ray spectroscopy examination. Thermal stability of the structures was determined by heating the samples to 700°C for different time intervals. The pure metals failed to make reliable contacts due to poor mechanical and chemical stability at high temperatures. In contrast, the metal silicides (MnSi and TiSi 2 ) showed superior chemical and mechanical stability after the thermal stability test. The observed contact resistance of MnSi and TiSi 2 was within the range of practical interest (10 −5 Ω cm 2 to 10 −4 Ω cm 2 ) over the entire range of investigated temperatures (20°C to 700°C). The best properties were found for the nanograined MnSi, for which the resistance of the contact was as low as 10 −6 Ω cm 2 .