Chin. Phys. B ›› 2013, Vol. 22 ›› Issue (12): 126301-126301.doi: 10.1088/1674-1056/22/12/126301

• CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES • 上一篇    下一篇

Investigations of high-pressure and high-temperature behaviors of the newly-discovered willemite-Ⅱ and post-phenacite silicon nitrides

陈东   

  1. College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China
  • 收稿日期:2013-03-23 修回日期:2013-05-13 出版日期:2013-10-25 发布日期:2013-10-25
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11005088 and 11105115), the Key Project of Henan Educational Committee, China (Grant No. 12A140010), and the Special Foundation for Young Teacher of Xinyang Normal University, China (Grant No. 2011084).

Investigations of high-pressure and high-temperature behaviors of the newly-discovered willemite-Ⅱ and post-phenacite silicon nitrides

Chen Dong (陈东)   

  1. College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China
  • Received:2013-03-23 Revised:2013-05-13 Online:2013-10-25 Published:2013-10-25
  • Contact: Chen Dong E-mail:chchendong2010@163.com
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11005088 and 11105115), the Key Project of Henan Educational Committee, China (Grant No. 12A140010), and the Special Foundation for Young Teacher of Xinyang Normal University, China (Grant No. 2011084).

摘要: Using the first-principles method of the plane-wave pseudo-potential, the structural properties of the newly-discovered willemite-Ⅱ Si3N4 (wⅡ phase) and post-phenacite Si3N4 (δ phase) are investigated. The α phase is predicted to undergo a first-order α→wⅡ phase transition at 18.6 GPa and 300 K. Within the quasi-harmonic approximation (QHA), the α→wⅡ phase boundary is also obtained. When the well-known β→γ transition is suppressed by some kinetic reasons, the β→δ phase transformation could be observed in the phase diagram. Besides, the temperature dependences of the cell volume,thermal expansion coefficient, bulk modulus, specific heat, entropy and Debye temperature of the involved phases are determined from the non-equilibrium free energies. The thermal expansion coefficients of wⅡ-Si3N4 show no negative values in a pressure range of 0-30 GPa, which implies that the wⅡ-Si3N4 is mechanically stable. More importantly, the δ-Si3N4 is found to be a negative thermal expansion material. Further experimental investigations may be required to determine the physical properties of wⅡ- and δ-Si3N4 with higher reliability.

关键词: first-principles, nitrides, phase boundary, thermal property

Abstract: Using the first-principles method of the plane-wave pseudo-potential, the structural properties of the newly-discovered willemite-Ⅱ Si3N4 (wⅡ phase) and post-phenacite Si3N4 (δ phase) are investigated. The α phase is predicted to undergo a first-order α→wⅡ phase transition at 18.6 GPa and 300 K. Within the quasi-harmonic approximation (QHA), the α→wⅡ phase boundary is also obtained. When the well-known β→γ transition is suppressed by some kinetic reasons, the β→δ phase transformation could be observed in the phase diagram. Besides, the temperature dependences of the cell volume,thermal expansion coefficient, bulk modulus, specific heat, entropy and Debye temperature of the involved phases are determined from the non-equilibrium free energies. The thermal expansion coefficients of wⅡ-Si3N4 show no negative values in a pressure range of 0-30 GPa, which implies that the wⅡ-Si3N4 is mechanically stable. More importantly, the δ-Si3N4 is found to be a negative thermal expansion material. Further experimental investigations may be required to determine the physical properties of wⅡ- and δ-Si3N4 with higher reliability.

Key words: first-principles, nitrides, phase boundary, thermal property

中图分类号:  (First-principles theory)

  • 63.20.dk
81.05.Je (Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)) 81.30.-t (Phase diagrams and microstructures developed by solidification and solid-solid phase transformations) 65.40.-b (Thermal properties of crystalline solids)