掺氧化钙及相变对高压下立方氧化锆电子结构和光吸收的影响

研究表明,立方氧化锆可作为冲击波实验中的窗口材料.为了使得该材料在常态下保持结构稳定,需添加稳定剂——氧化钙.然而,掺杂会导致其在29 GPa的冲击压力下从立方转变为斜方Ⅱ结构相.因此,该材料在冲击压缩下的电子结构和光学吸收性质以及作为光学窗口的适用压力范围是值得研究的重要问题.本文运用第一性原理的方法,分别计算了在100 GPa范围内两种结构氧化锆的电子结构和光学吸收性质.结果表明:(1)在立方结构相区,冲击压力将导致其吸收边蓝移,而在斜方Ⅱ结构相区,却使得其吸收边红移;(2)在立方结构相区,掺杂将引起能隙变窄(吸收边红移),但对于斜方II相区,却导致能隙变宽(吸收边蓝移);(3)冲击结构相变使得能隙变窄,吸收边红移.本文数据建议,掺氧化钙的立方氧化锆在95GPa的冲击压力范围内可作为光学窗口材料.

Effects of CaO-doping and the phase transition in cubic Zirconia on its electronic structure and optical-absortption property at high pressure

It is shown that cubic zirconia can be used as a window material in shock wave experiments. A stabilizer, calcium oxide, is needed to be added into this material to maintain its structural stability at ambient conditions. However, CaO-doping may cause a cubic-to -orthorhombic II phase transition in Zirconia occurring in a shock pressure of 29 GPa. Therefore, the electronic structure and optical-absorption property of CaO-ZrO2 under shock compression as well as the shock-pressure range as the optical window are some important issues. Here, electronic structure and optical-absorption property of pure and CaO-doped Zirconia with two crystal structures within 100 GPa were calculated using first-principles methods, respectively. The results show that: (1) the shock pressure leads to the blue-shift of the absorption edge in the cubic-phase region but its red-shift in orthorhombic II phase region; (2) the doping causes a band-gap decrease in the cubic-phase region but its increase in orthorhombic II phase region; (3) the shock phase-transition may cause an reduction in band gap and the red-shift of the absorption edge. The calculated data suggest that within the shock-pressure range of 95 GPa the CaO-ZrO2 can be used as optical window material.