REACTION OF RARE-EARTH-METALS WITH BORON AND ALUMINUM

We have used x-ray phase analysis to establish the phase equilibria at 600 degrees C for the systems Gd-Al-B, Tb-Al-B, and Ho-Al-B (the boron-rich sites have nor yet been studied). We determined the crystalline structure of the new borides HoAlB4 and ErAlB4 (space group Pbam, YCrB4 type, a = 59283(7), b = 1.1553(1), c = 0.35306(5) mm for HoAlB4 and a = 0.59955(9), b = 1.1487(2), c = 0.35284(8) nm for ErAlB4). We synthesized the compound Tm1-xAl1-yB14 with MgAlB14 type structure (space group Imma, a = 0.5826(2), b = 1.0380(2), c = 0.8176(2) nm) by the method of crystallization from an aluminum melt.