It showed that the 20Eu sample contain a broad range of Eu-ion coordination modes with a significantly increased fraction of Eu-ions in the very low four-and five-coordination to oxygen, compared to the 5Eu sample which clusters were dominated by five-and six-coordinated Eu-ions, yielding typical average Eu CN of 5.2-5.5. However, it cannot be ruled out that there might also be higher coordinated Zn 2+ -ions present, which based on the reported ionic radii of Zn 2+ (0.88 Å) and O 2-(1.40 Å) could have Zn-O bond distances of up to 2.28 Å for the six-coordinated Zn 2+ -ions. This distance would overlap with the shortest distances for the four-coordinated Eu 3+ions. Thus, the ePDF for the 5Eu sample gave results in good agreement with the previously obtained theoretical 4.1Eu structures with 4 or 8 Eu atom oxide clusters occupying space in the h-ZnO crystal with nearly no effect on its unit cell-dimensions. Interestingly, it was found that the 20Eu sample, while being similar to the 5Eu sample for the longer Eu-O bond-lengths, showed a substantial increase in Eu-ions coordinated to the very low four and five oxygen. However, the atom-atom distances of the four-coordinated Eu-ions overlap those of fiveand six-coordinated Zn-ions and therefore it cannot be ruled out that the 20Eu sample also contained some higher Zn-ions coordination numbers than present in ZnO.