Typical versus plots at different pressures. The experimental data are denoted by red circles and the blue lines indicate the fitting straight lines in the form of y = a + bx, where a and b stand for (λ/d)2 and (2 t)2 in Eq. (6), respectively. The values of R 2 are 0.987, 0.963, and 0.979 at 3.30 GPa, 16.14 GPa, and 24.93 GPa, respectively.
The pressure dependence of compressive strength t derived from the diffraction profile width analysis. The lines are not the fitting lines but just guide for the eyes only. The compressive strength increases quickly with pressure below 3.30 GPa, while its increase is less pronounced at higher pressures. The standard error of compressive strength arises from the least square fitting uncertainty of the slope of the (2whkl cosθhkl )2 vs sin2 θ/E(hkl)2 plots, i.e., (2t)2. The error bars on either side equal to the standard errors.
Plot of the Rietveld refinement for CeO2 at 1.46 GPa and ambient temperature (λ = 0.6199 Å). The experimental data are denoted by blue circles and the calculated pattern is presented by red solid line. The lower green line is the difference between the observed and calculated patterns. Vertical tricks mark the positions of the reflection of CeO2 in fluorite phase.
The measured equation of state of fluorite type CeO2 at ambient temperature. Our results of bulk CeO2 are presented by solid symbols. Green pentagrams indicate the result derived from Rietveld refinement by GSAS+ EXPGUI Rietveld package. Red spheres are the estimation results of a p 3 by diffraction profile widths analysis and later iteration procedure. The open squares are the result of Wang et al. 13 that derived from nano-CeO2. The asterisks indicate the result of Gerward et al. 11 derived from bulk CeO2 using energy dispersive x-ray diffraction technology. Our two sets of result are fitted with Vinet EOS and denoted as green dash line and red solid line, respectively.
The values of α varied with pressure. The lower panel was the difference between α 0 and α 1.
Summary of the experimental results of CeO2. a m is the result determined from Rietveld refinement.
Bulk modulus and its pressure derivative of CeO2. The bold values were fixed during the fitting procedure.
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