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Phase relations and hardness trends of ZrO_2 phases at high pressure

机译：高压下ZrO_2相的相关系和硬度趋势

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We use high-resolution synchrotron x-ray powder diffraction and density-functional theory (DFT) to investigate the phase stability, equations of state (EOSs), and mechanical hardness of zirconia (ZrO_2) up to ～54 and 160 GPa, respectively. For the equilibrium phase at ambient conditions (MI), we provide an experimental EOS that is comparable to results obtained from room-pressure Brillouin scattering experiments and bulk modulus-volume systematics but different from previous high-pressure experiments. The experimental second-order Birch-Murnaghan EOS parameters of MI-ZrO_2 are: ambient-pressure volume (V_0) of 35.15(±0.03) A~3/f.u. with an ambient-pressure bulk modulus K_0 of 210(±28) GPa. For the high-pressure OI phase, we find that the K_0=290(±11) GPa, which is 19%-32% higher than previously determined, and V_0=33.65(±0.07) A~3/f.u. The small volume decrease of 3.4% across the MI→OI transition at ～10 GPa is associated with a 38% increase in the bulk modulus consistent with our DFT calculations that predict a ～36% and 39% increase in K_0 for the generalized gradient and local density approximations, respectively. In contrast to the EOS of MI and OI, we find that our experimental EOS for the high-pressure OII phase is in good agreement with previous measurements. The large volume decrease across the OI→OII phase transition as obtained from both our experiments and calculations is ～10%. Our estimates, using scaling relations, indicate that this phase, while dense and quenchable, may have a comparatively low mechanical hardness of ～ 10 GPa.
机译：我们使用高分辨率同步加速器X射线粉末衍射和密度泛函理论（DFT）分别研究了分别高达约54 GPa和160 GPa的氧化锆（ZrO_2）的相稳定性，状态方程（EOSs）和机械硬度。对于环境条件（MI）下的平衡相，我们提供了一个实验EOS，该EOS与从室温布里渊散射实验和体积模量-体积系统学获得的结果相当，但与以前的高压实验不同。 MI-ZrO_2的实验二阶Birch-Murnaghan EOS参数为：环境压力体积（V_0）为35.15（±0.03）A〜3 / f.u。的环境压力体积模量K_0为210（±28）GPa。对于高压OI相，我们发现K_0 = 290（±11）GPa，比先前确定的值高19％-32％，而V_0 = 33.65（±0.07）A〜3 / f.u。在大约10 GPa的MI→OI过渡期间，体积小幅下降3.4％与体积模量增加38％有关，这与我们的DFT计算相符，DFT计算预测，对于广义梯度，K_0分别增加〜36％和39％。局部密度近似值。与MI和OI的EOS相比，我们发现高压OII相的实验EOS与以前的测量非常吻合。根据我们的实验和计算，在OI→OII相变过程中，体积减小的幅度很大，约为10％。我们使用比例关系进行估算，表明该相虽然致密且可淬火，但其机械硬度可能较低，约为10 GPa。

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