LSPM-CNRS, Université Paris Nord, 93430 Villetaneuse, France.
Sci Rep. 2013;3:2351. doi: 10.1038/srep02351.
Solid-state phase transformations and melting of high-purity crystalline boron have been in situ and ex situ studied at pressures to 20 GPa in the 1500-2500 K temperature range where diffusion processes become fast and lead to formation of thermodynamically stable phases. The equilibrium phase diagram of boron has been constructed based on thermodynamic analysis of experimental and literature data. The high-temperature part of the diagram contains p-T domains of thermodynamic stability of rhombohedral β-B106, orthorhombic γ-B28, pseudo-cubic (tetragonal) t'-B52, and liquid boron (L). The positions of two triple points have been experimentally estimated, i.e. β-t'-L at ~ 8.0 GPa and ~ 2490 K; and β-γ-t' at ~ 9.6 GPa and ~ 2230 K. Finally, the proposed phase diagram explains all thermodynamic aspects of boron allotropy and significantly improves our understanding of the fifth element.
已在 1500-2500 K 的温度范围内原位和异位研究了高纯结晶硼的固态相变和熔融，在该温度范围内扩散过程变得很快，导致形成热力学稳定的相。基于实验和文献数据的热力学分析，构建了硼的平衡相图。该相图的高温部分包含了热力学稳定的三方晶系β-B106、正交晶系γ-B28、拟立方（四方）t'-B52 和液态硼（L）的 p-T 域。通过实验估计了两个三相点的位置，即β-t'-L 在约 8.0 GPa 和约 2490 K；β-γ-t' 在约 9.6 GPa 和约 2230 K。最后，所提出的相图解释了硼同素异形体的所有热力学方面，显著提高了我们对第五种元素的理解。
