CRYSTAL-GROWTH OF VANADIUM SILICIDES FROM HIGH-TEMPERATURE METAL SOLUTIONS AND SOME PROPERTIES OF THE CRYSTALS

Crystals of vanadium silicides were grown from high-temperature tin an d copper solutions in an argon atmosphere using vanadium metal chips a nd silicon powder as starting materials. The crystals grown were V3Si, V5Si3 and VSi2. The growth conditions for obtaining single crystals o f relatively Large size were established. The as-grown V3Si, V5Si3 and VSi2 crystals were used for chemical analysis and measurements of uni t cell dimensions. Densities, microhardness and electrical resistivity were determined on V5Si3 crystals, and oxidation at high temperature in air was studied for V5Si3 and VSi2 crystals. The microhardness valu e on (110) planes of V5Si3 is 12.3 (+/-0.1) Gpa. The electrical resist ivity determined on V5Si3 crystal is 17.6 (+/-0.7) mu Omega cm. The ox idation of V5Si3 and VSi2 crystals begins to proceed at a measurable r ate in the temperature range of about 355 and 515 degrees C, respectiv ely. The final oxidation product is V2O5. In all cases, non-crystallin e SiO2 seemed to be formed during the oxidation reaction.