GROWTH-CONDITIONS OF TA3B4 SINGLE-CRYSTALS PREPARED BY THE ALUMINUM-FLUX METHOD

Tantalum boride crystals have been prepared from high temperature aluminium solution using tantalum and boron powders as starting materials in an argon atmosphere. The growth conditions for obtaining relatively large crystals of Ta3B4 in a pure form containing no extra phases were established. The optimum growth conditions for growing Ta3B4 single crystals are the following: Atomic ratios of starting materials B/Ta = 1.33 and Al/Ta = 16.77, soaking temperature 1650-degrees-C, soaking time 5 h and cooling rate 25-degrees-C h-1. The single crystals of Ta3B4 display a grey color, metallic cluster, and a trapezoidal shape, The largest crystals prepared have dimensions of about 0.37 mm X 0.37 mm X 0.40 mm. The crystals are orthorhombic with space group Immm and unit cell dimensions a = 3.2914(8), b = 13.994(3), c = 3.1327(6) angstrom, and V = 144.29(8) angstrom 3. The X-ray density is 13.490(3) g cm-3.