Some peculiarities of eutectic crystallization of LaB6-(Ti, Zr)B-2 alloys

The structures of eutectic LaB6(Ti, Zr)B-2 alloys are studied after directi onal crystallization. The eutectic compositions and monovariant equilibrium between two quasibinary eutectics in this system were determined. Varying the TiB2/ZrB2 borides ratio permits us to control in their solid solutions the corresponding cell dimensions and, consequently, the boron-boron distan ces in the resulting quasibinary borides, Our previous assumptions that the perfectness of the real structure is determined by differences in the dist ances between boron atoms in boron sublattices of hexa- and diboride phases were confirmed. It is shown that forming the regular whiskers structure is much easier for complex (Ti,Zr)B-2 boride than for individual TiB2 or ZrB2 borides, (C) 2000 Academic Press.