“…The XPS 3d spectra of Pr in (Ce,Pr,Sm)O and (Ce,La,Pr,Sm,Y)O resemble the one obtained for Proxide confirming that oxidation state of Pr is the same in all powders. Comparing the XPS data for Pr-oxide obtained in this work (Figure 2(b)) to the one reported in the literature, [27,28] the spectra indicate the presence of Pr 4+ rather than Pr 3+ , but mixed oxidation state [29] cannot be excluded. At present, based on XRD data (see SI, Figure S2b and S2c), it can only be assumed that Pr is most probably present in mixed oxidation state (Pr 4+ and Pr 3+ ).…”