| What they have produced is clearly not LK-99. They write that:
"
As shown in Figure 9, the x-ray diffraction spectrum of the
ground powder of the finally sintered product is highly consistent with the x-ray diffraction
spectrum reported by Lee et al.[3] and coincides well with the diffraction pattern of the apatite.
This proves that we have successfully synthesized the modified lead-apatite as Lee et al.[3.4]
" (First off, you need to pay to the spectrum swear jar. an XRD pattern is a pattern, not a spectrum, it resolves space, not energy.) But looking at figure 9 shows that the material is not the same.
They are missing a peak at ~17.5 degrees, and have an extra one around 25 degrees. Further, all the peaks seem to be shifted about the same amount from the LK-99 structure, as the LK-99 is from pure lead-apatite.
This indicates that they have an even smaller unit cell. So if the .5% compression in the original LK-99 paper is correct, there could easily be an overcompression present in this article. All the XRD pattern tells you is that they produced something wrong, an that it did not superconduct. It makes it impressive how pure the phase was in the original LK-99 paper. I will however say that there are some problems with the XRD pattern in the original paper too:
They did not write which energy the XRD was measured at, one would then guess that it is Cu-Ka, but who knows.
Under any circumstances, a peak should not be missing completely from a powder measurement (if it was a pellet, it could be missing due to orientation effects) |
There are strong similarities between the XRD patterns, but considering the theoretical paper yesterday about selective site substitution being necessary to achieve superconductivity, it's reasonable to suspect that these "minor" differences may be critical.