Compression behavior and phase transition of β-Si₃N₄ under high pressure

【摘要】 The compressibility and pressure-induced phase transition of β-Si₃N₄ were investigated by using an angle dispersive x-ray diffraction technique in a diamond anvil cell at room temperature. Rietveld refinements of the x-ray powder diffraction data verified that the hexagonal structure（with space group P63/m, Z = 2 formulas per unit cell） β-Si₃N₄ remained stable under high pressure up to 37 GPa. Upon increasing pressure, β-Si3 N4 transformed to δ-Si₃N₄ at about 41 GPa. The initial β-Si₃N₄ was recovered as the pressure was released to ambient pressure, implying that the observed pressureinduced phase transformation was reversible. The pressure–volume data of β-Si₃N₄ was fitted by the third-order Birch–Murnaghan equation of state, which yielded a bulk modulus K₀= 273（2） GPa with its pressure derivative K₀= 4（fixed）and K0= 278（2） GPa with K 0= 5. Furthermore, the compressibility of the unit cell axes（a and c-axes） for the β-Si₃N₄ demonstrated an anisotropic property with increasing pressure.更多还原

【Abstract】 The compressibility and pressure-induced phase transition of β-Si₃N₄ were investigated by using an angle dispersive x-ray diffraction technique in a diamond anvil cell at room temperature. Rietveld refinements of the x-ray powder diffraction data verified that the hexagonal structure（with space group P63/m, Z = 2 formulas per unit cell） β-Si₃N₄ remained stable under high pressure up to 37 GPa. Upon increasing pressure, β-Si3 N4 transformed to δ-Si₃N₄ at about 41 GPa. The initial β-Si₃N₄ was recovered as the pressure was released to ambient pressure, implying that the observed pressureinduced phase transformation was reversible. The pressure–volume data of β-Si₃N₄ was fitted by the third-order Birch–Murnaghan equation of state, which yielded a bulk modulus K₀= 273（2） GPa with its pressure derivative K’₀= 4（fixed）and K₀= 278（2） GPa with K’₀= 5. Furthermore, the compressibility of the unit cell axes（a and c-axes） for the β-Si₃N₄ demonstrated an anisotropic property with increasing pressure.更多还原