Abstract
Different polytypes of SiC are described and predicted in literature. Here, we report the first occurrence of an orthorhombic 6O-SiC polytype as rock-forming mineral in the nickel laterite mine of Tiebaghi (New Caledonia). This new class of SiC crystallizes in the space group Cmc21 with 12 atoms per unit cell [a = 3.0778(6) Å, b = 5.335(2) Å, c = 15.1219(6) Å, α = 90°, β = 90°, γ = 120°]. The density of 6O-SiC is about 3.22 g/cm3 and the calculated indirect bandgap at room temperature of 3.56 eV is identical to 6H-SiC. Our results suggest that 6O-SiC is the intermediate state in the wurtzite to rocksalt transformation of 6H-SiC.
Highlights
Different polytypes of SiC are described and predicted in literature
SiC is a highly attractive material for fabrication of microelectronic and optoelectronic devices due to its outstanding physical properties, such as a wide bandgap, high thermal conductivity coupled with low thermal expansion
Different grains of moissanite have been found and separated from the porosities of siliceous breccia originating from hydrofracturing of peridotites at Tiebaghi mine in New Caledonia (Fig. 1a)
Summary
Different polytypes of SiC are described and predicted in literature. Here, we report the first occurrence of an orthorhombic 6O-SiC polytype as rock-forming mineral in the nickel laterite mine of Tiebaghi (New Caledonia). The structural, elastic and electronic properties of this new class of SiC were studied by single crystal X-rays diffraction, Raman spectroscopy and ab initio DFT calculation. It is found by ab initio calculations that 6H polytype under high temperature-pression undergoes a transition to the www.nature.com/scientificreports
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