Growth Conditions of Nb3Si, α-Nb5Si3 and NbSi2 Single Crystals from High-Temperature Metal Solutions and Properties of the Crystals

Abstract

Nt>3Si (cubic), a-NbsSis and NbSi2 single crystals were prepared from high temperature tin or copper solutions using niobium metal powder and silicon powder as starting materials under an argon atmosphere. The growth conditions for obtaining single crystals of relatively large size were established. The results of chemical analysis and measurements of the unit cell dimensions and densities (d m ) are as follows: From Sn solution: for a-NbsSia (NbsSiß.os) ο = 6.5703(2) Ä, c = 11.8848(6) Ä, d m = 7.06(4) gem" 3 ; for NbSi 2 (NbSii.97) a = 4.7968(7) A, c = 6.5901(5) A, d m = 5.60(4) gem" 3 .From Cu solution: for Nt^Si, a = 4.2104(9) A; for a-Nb 5 Si 3 (Nb 5 SI 3 .oo) a = 6.5695(8) A, c = 11.8873(9) A, d m = 7.07(3) gem" 3 .The electrical resistivity (p) determined on NbsSi3 and NbSi2 crystals are as follows: for a-NbsSi3: ρ = 182 μ Ω · cm; for NbSi 2 : ρ = 1250 μ Ω • cm.The oxidation of a-NbsSis and NbSi2 crystals begins to proceed at a measurable rate in the temperature range of about 430°C and 520°C, respectively. The final oxidation product is Nl^Os. In all cases, non-crystalline S1O2 seemed to be formed during the oxidation reaction.

Effect of Product Conductivity on Field‐Activated Combustion Synthesis

“…This material was chosen because ture is too low to effect a self-sustaining combustion wave. 1 In of its relatively high conductivity 10 and because of previous contrast, those kinetically limited have high adiabatic temperaobservations on its synthesis by field-activated SHS. 11 Despite tures but still cannot sustain a self-propagating wave.…”