β-SiN Microcrystals Prepared by Carbothermal Reduction-Nitridation of Quartz.

Single phase β-SiN with microcrystals was synthesized via carbothermal reduction-nitridation (CRN) of quartz and carbon coke powder as starting materials. The effects of reaction parameters, i.e., heating temperature, holding time, C/SiO ratio, FeO additive and β-SiN seeds on the phase transformation and morphology of products were investigated and discussed. Rather than receiving a mixture of both α- and β- phases of SiN in the products, we synthesized powders of β-SiN single polymorph in this work. The mechanism for the CRN synthesis of β-SiN from quartz and the formation mechanism of FeSi droplets were discussed. We also firstly reported the formation of FeSi Archimedean solids from a CRN process where FeO was introduced as additive. Comparing to the gear-like short columnar morphology observed in samples without β-SiN seeding, the addition of β-SiN seeds led to an elongated morphology of final products and much finer widths. In addition, the β-SiN microcrystals exhibited a violet‒blue spectral emission range, which could be highly valuable for their future potential optoelectronic applications.