Analysis of electrical resistivity of compositions within the Mo-Si-B ternary system, part I: single phase compounds

Electrical resistivity of nominally single phase polycrystalline compositions within the Mo-Si-B system was characterized as a function of temperature within the range of 25–1500°C. The samples were characterized by X-ray diffraction, and the experimental lattice parameters are shown to agree with literature values. Mo5SiB2 (T2), MoB, Mo3Si and Mo5Si3 all possess a similar temperature coefficient of resistivity (TCR). T1 phase (Mo5+ySi3−yBx) exhibited a higher resistivity and lower TCR at all temperatures than the parent Mo5Si3. Hall effect measurements showed that boron in T1 is electrically active, increasing the electron concentration an order of magnitude beyond that of Mo5Si3. The higher carrier concentration in T1 is thought to be responsible for the observed difference in TCR between the two phases, while microcracking in T1 is believed responsible for the higher resistivity. MoSi2 was found to have a significantly higher TCR compared with all other compositions in this study. The resistivity of all phases is consistent with a description based on semi-metals or low density of states metals.