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

Electrical resistivity of nominally single phase polycrystaline composition s within the Mo-Si-B system was characterized as a function of temperature within the range of 25-1500 degreesC. The samples were characterized by X-r ay diffraction, and the experimental lattice parameters are shown to agree with literature values. MO5SiB2 (T2), MOB. Mo,Si and Mo,Si, all possess a s imilar temperature coefficient of resistivity (TCR). T1 phase (Mo5+ySi3-yBy ) exhibited a higher resistivity and lower TCR at all temperatures than the parent Mo5Si3. Hall effect measurements showed that boron in T1 is electri cally active, increasing the electron concentration an order of magnitude b eyond that of Mo,Si,. The higher carrier concentration in T1 is thought to be responsible fbr the observed difference in TCR between the two phases, w hile microcracking in T1 is believed responsible for the higher resistivity . MoSi2 was found to have a significantly higher TCR compared with all othe r compositions in this study. The resistivity of all phases is consistent w ith a description based on semi-metals or low density of states metals. (C) 2001 Elsevier Science B.V, All rights reserved.