Ternario si - ni- n

JOURNAL

OF SOLID

STATE

CHEMISTRY

70, 178-184 (1987)

Phase Diagrams

of the Ternary

Systems

Mn, Fe, Co, Ni-Si-N*

F. WEITZER AND J. C. SCHUSTER Institut fiir Physikalische Chemie, Universitiit Wien, Wtihringerstrasse 42, A-1090 Vienna, Austria
Received December 20, 1986

Phase equilibria in the ternary systems Mn, Fe, Co, and Ni-Si-N are investigated and isothermal sections at 900°C (Fe-Si-N, Ni-Si-N), at 1000°C(Mn-Si-N, Co-Si-N) and at 1150°C(Fe-Si-N) are presented. In the system Mn-Si-N, S&N4 coexists with MnSiN2, Mn,Si, Mn& MnSi, and MnSizmX. In the systems Fe, Co, Ni-Si-N, S&N4 coexists with all binary silicides but reacts rapidly with iron above 1120 f lO”C, and cobalt and nickel above 1170 2 10°C to form binary silicides and nitrogen gas. 0 1987 Academic Press, Inc

rhombic, space group Pna2,, a = 0.5258 nm, b = 0.6511 nm, and c = 0.5070 nm (4). Silicon nitride is one of the most attrac- MnSiN2 was found to form as well by tive advanced ceramic materials of today. reaction of manganese with silicon under Although much is known regarding wetting, nitrogen (3). The decomposition of MnSiN2 metallizing, and joining S&N4 to base met- into MnSi and N2 gas starts under nitrogen als no rationale of these data in the form of (IO’ Pa) above 1300°C and under argon phase diagrams is available. This prompted above 800°C (3). Silicon nitride is reported to decompose a systematic investigation of such transition metal-silicon-nitrogen systems and the in contact with iron at temperatures above first set of ternary phase diagrams is pre- 700°C (5). This reaction is described to be fast and violent at higher temperatures, sented here. especially above the melting point of iron (1, 2, 6). At 12OO”C, S&N4 whiskers are Literature Review observed to be dissolved in an Fe matrix Liquid manganese wets silicon nitride (29 (7). The reaction products found are binary iron silicides and nitrogen gas. A tempera= 74”) (I) and is reported to react violently