PREPARATION OF SINGLE-CRYSTALS OF THE RARE-EARTH BORIDES BY THE SOLUTION METHOD AND A STUDY OF THEIR PROPERTIES

Single crystals of LaB6, SmB6, SmB4, EuB6 and YbB6 were prepared by crystallization from solutions in molten aluminium. Their compositions, lattice parameters, microhardnesses and etch pit densities were determined. Single crystals of LaB6 prepared by the solution method were shown to be more perfect than zone-melted crystals. For EuB6 and LaB6 single crystals the dependence of the specific electrical resistance on hydrostatic pressure (up to 15 kbar) was measured. The electrical resistance of EuB6 was observed to decrease markedly with an increase in the pressure; this may be due to an increase in the number of Eu3+ ions. A comparison of the electrical and galvanomagnetic properties of EuB6 single crystals (prepared both by the solution method and by the floating-zone technique) with the electrical and galvanomagnetic properties of poly crystalline samples was made. The discrepancy between these properties is assumed to arise from the different number of Eu3+ ions which is dependent on the preparation method. © 1979.