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

Abstract

The melting behavior of 13-SiC with diamond structure was investigated under high pressures up to about 10 GPa using a flashheating device. The peritectic temperature, at which the SiC decomposes into two phases of carbon saturated liquid Si and solid carbon (graphite) by a peritectic reaction , increases with pressure and the formation temperature of one liquid phase (1-SiC) also tends to increase with pressure. The solubility of carbon in liquid Si reach 50% at about 10 GPa and a-SiC melts directly into 1-SiC. [silicon carbide, melting temperature, peritectic reaction, carbon solubility, electrical resistivity]

High-Pressure, High-Temperature Behavior of Silicon Carbide: A Review

“…The ambient pressure decomposition of SiC into solid C plus liquid Si begins at~2840 K in experiments [19] but is predicted to occur at higher temperatures of 3100 K in computations [104,105]. Prior to recent diamond-anvil cell work up to~80 GPa [18], explorations of high-pressure melting and decomposition have gone up to~10 GPa while heating to temperatures as high as 3500 K [17,[106][107][108][109][110]. Although confusion has arisen as to the nature of SiC melting at lower pressures, higher pressure studies indicate that 3C-SiC continues to decompose at high temperature, at least up to the transition to the rocksalt structure at~60 GPa.…”

On melting of silicon carbide under pressure

“…Fig. 1 SiC melting temperature according to the literature data [1][2][3][4][5][6][7]. Solid symbols correspond to the incongruent melting, open symbol indicates the congruent melting.…”

“…close to ambient, the temperature of SiC incongruent melting may be evaluated at 3100±40 K [1,2], while data on its melting under high pressure are very limited [3][4][5][6][7] and extremely contradictory ( Fig. 1), which does not allow one to make any conclusions about the melting behavior (congruent or incongruent) and the slope of the melting curve.…”

“…Solid symbols correspond to the incongruent melting, open symbol indicates the congruent melting. In papers [3][4][5][6][7] the errors of melting temperature determination were not estimated. …”

“…Melting of large single crystals was indicated by a change of the shape and microstructure. In the case of small crystals the appearance of a liquid phase in the system was fixed either by the formation of a strong monolith sample with a pronounced laminar structure after quenching (samples, which did not achieve the melting temperature, remained brittle compacts of relatively large crystals) or in situ from a jump of the cell electrical resistance caused by a change of conductivity type from the semiconducting (solid SiC) to the metal one (melt) [3,4,10]. In the second case boron nitride capsules were not used and the sample was in a direct contact with a graphite heater.…”