Catalytic Effects of Metals on Direct Nitridation of Silicon

Abstract

Catalytic effects were investigated on the direct nitridation of silicon granules, impregnated with 0.125–2.0% by mass of calcium, yttrium, iron, copper, silver, chromium, or tungsten, in a stream of nitrogen with 10% hydrogen, using a tubular flow reactor operated at temperatures ranging from 1200° to 1390°C. Calcium and yttrium suppressed the formation of β‐silicon nitride while iron enhanced the formation of β‐silicon nitride over the temperature range investigated. An addition of 0.125% calcium resulted in about 99% overall conversion with 100%α‐phase and a 2.0% yttrium addition yielded an overall conversion over 98% with an α‐phase content above 97%. Copper promoted not only the nitridation but the formation of α‐silicon nitride at 1200°C, but enhanced the β‐phase formation at higher temperatures. The role of liquid phases on the formation of α‐/β‐silicon nitride was also discussed based on the nitridation of silicon impregnated with copper, calcium, silver, chromium, and tungsten.