The Influence of Chromium Oxide on the Sintering Behavior of Silicon Nitride. (18th July 2012)

• Record Type: Journal Article
• Authors: Alem, Ali; Pugh, Martin D.
• Is Part Of: International journal of applied ceramic technology. Volume 10(2013)Supplement 1
• Page Start: E258
• Page End: E266
• Publication Date: 2012-07-18
• Subjects: Ceramics -- Periodicals; Ceramics -- Technological innovations -- Periodicals; 620.1405
• DOI: 10.1111/j.1744-7402.2012.02814.x
• Languages: English
• ISSNs: 1546-542X

Abstract

Abstract : In this study, pressureless sintering of silicon nitride via the addition of chromium oxide was investigated. Silicon nitride samples containing additives from the Cr–Cr2 O3 –SiO2 system were sintered under different conditions. The phase transformation, the degree of densification and the in situ reactions between Si3 N4 and chromium compounds were investigated and the reactions were validated thermodynamically. It was found that Si3 N4 reacts with Cr2 O3 and Cr and these in situ reactions lead to Si3 N4 decomposition and consequently formation of a series of chromium silicides including Cr3 Si, Cr5 Si, and CrSi2 . Due to the presence of chromium silicides as liquid phases during sintering, the α‐Si3 N4 to β‐Si3 N4 phase transformation started around 1400°C and was completed around 1800°C. On the other hand, densification of Si3 N4 samples with chromium oxide addition was not observed. The participation of Cr2 O3 in these in situ reactions prevents sufficient formation of chromium silicate and leads to insufficient liquid phase with poor wettability during sintering, resulting in poor densification.