Lanthanum-silicon system

By using differential thermal analysis, metallography and X-ray examination, the La-Si phase diagram was constructed. La5Si3, La3Si2, La5Si4, LaSi were confirmed. Two lanthanum disilicides were found - LaSi2-a1 (structure type alpha -GdSi2) and LaSi2-a2 (structure type alpha -ThSi2), the two-phase region LaSi2-a1 + LaSi2-a2 being very narrow. The LaSi and LaSi2-a1 intermetallics melt congruently at 1620 and 1730 degreesC, respectively. La5Si3, La3Si2, La5Si4 and LaSi2-a2 form in peritectic reactions at 1260, 1470, 1570 and similar to 1600 degreesC, respectively. Three eutectics occur at 722 +/-9 (11 at.% Si), 1528 +/-9 (55.5 at.% Si) and 1205 +/-7 degreesC (82 at.% Si). (C) 2001 Elsevier Science BV All rights reserved.