The Constitution of the Silicon‐Carbon System

Abstract

Constitution (Phase Equilibria) / Refractories / ThermodynamicsThe constitution of the Si-C system was re-investigated between 1400 and 3000°C using an arc-melting furnace and a 350 kHz induction furnace with two pyrometric temperature measurement devices. The experiments were performed in specially designed graphite crucibles in order to avoid the falsification of temperature measurements by the arising vapour species. The samples were further characterized by high temperature DTA and by X-ray diffraction and X-ray microanalysis. One intermediate compound, Sic, occurs in the system. Si and SIC form a degenerate eutectic system; the eutectic temperature and composition are 1413 "C and 0.02 at.% C, resp. Peritectic formation of Sic was observed at 2830°C according to the reaction [Sio~,,Co,,3)+(C) = 6iC). The melt boils incongruently under 1 bar pressure at about 3000°C. The condensed vapour consists of Si and S i c containing altogether 40 atPlo C. Sic is monotropic. Metastable, cubic /3-SiC is formed from the gas phase and from the melt according to Ostwald's rule. Hexagonal a-Sic seems to be the stable modification in the overall temperature range.

Melting Behavior of .BETA.-SiC at High Pressure.

“…This difference raises interesting question about the nature of the liquid state of silicon carbide (SiC), which is an alloy of these two elements with above competing phenomena. [6,7] as well as the thermodynamical stability of a -and ƒÀ-SiC.…”

Effect of pulsed laser irradiation on the SiC surface

“… During the laser pulse (10‐50 ns) in air, the laser affected zone (˜200‐300 nm) reached very high temperatures, well above the melting temperature of SiC. At about 2830°C, Figure , incongruent melting of SiC leads to the formation of a Si‐rich liquid and C. …”

Metastable Solvent Epitaxy of SiC, the Other Diamond Synthetics

“…Furthermore, it also mentioned on the report of Verma & Krishna (1966), the existence of α stability above 2000 • C. On the other hand, Fromm & Gebhardt (1976) reported the different type of phase diagram as shown in Fig. 11, wherethephasetransitionfromβ to α phases occurs at around 2000 • C. Solubilities of carbon in liquid silicon measured by Hall (1958), Scace & Slack (1959), Dash (1958), Dolloff (1960, Nozaki et al (1970), Oden & McCune (1987), Suhara et al (1989), Kleykamp & Schumacher (1993), Iguchi & Narushima (1993), Ottem (1993), and Yanabe et al (1997) are summarized as in Figs. 12.…”