GROWTH AND PROPERTIES OF CR3SI AND CR5SI3 SINGLE-CRYSTALS BY THE COPPER-FLUX METHOD

The single crystals of Cr3Si and Cr5Si3 were prepared by the high temperature copper solution method using metal chromium and silicon powders as starting materials in an argon atmosphere. The conditions for obtaining these crystals with one-phase materials and a relatively large size were determined. As grown Cr3Si and Cr5Si3 single crystals were used for chemical analysis, and measurements of unit cell dimensions, Vickers microhardness and electrical resistivity. The optimum conditions for growing Cr3Si and Cr5Si3 single crystals are the following atomic ratios of starting materials (Si/Cr, Cu/Cr), soaking temperature and soaking time; Si/Cr = 0.3 approximately 1.0, Cu/Cr = 4.8 approximately 28.8, 1400-degrees-C and 10 h for Cr3Si and Si/Cr = 4.0 approximately 4.5, Cu/Cr = 14.4 approximately 19.2, 1400-degrees-C and 10 h for Cr5Si3, respectively. Under these conditions, Cr3Si single crystals, having a silver color and metallic luster, were generally bounded by {110} planes. On the other hand, Cr5Si3 single crystals, having a silver color and metallic luster, were generally obtained in the form of prismatic shape extending to <100> direction. The largest crystals prepared have maximum dimensions of about 1.7 mm x 1.7 mm x 1.7 m (for Cr3Si) and 0.3 mm x 0.3 mm x 11.2 mm (for Cr5Si3). The results of chemical analysis and the measurements of unit cell dimension, Vickers microhardness (H(V)) and electrical resistivity are as follows: Cr2.6Si approximately Cr3.5Si, a = 4.551 (1) approximately 4.557 (1) (A), H(V) = 1410 +/- 20 kgf/mm2 and rho = 1.98 x 10(-4) approximately 3.23 x 10(-4) OMEGA.cm for Cr3Si; Cr5.7Si3, a = 9.148 (5) and c = 4.643 (2) (angstrom), H(V) = 1360 +/- 50 kgf/mm2 and rho = 2.80 x 10(-2)OMEGA.cm for Cr5Si3.