| Abstract Scope |
A fast salt-based synthesis route to nano-crystalline ZnO:Eu (0-20% EuO1.5) sponges built of ca. 10 nm sized ZnO:Eu crystallites is presented. The phase-development from 200 to 900 oC was investigated by TG, DSC, XRD, IR spectroscopy, SEM, TEM, XPS, and EXAFS. The ZnO:Eu sponges obtained at up to 600 oC showed only peaks of hex-ZnO with unit cell-dimensions very close to the un-doped ZnO. In the range 700-1000 oC, phase separation took place yielding c-Eu2O3 nano-crystals. The nature and even existence of such high doping levels of the large Eu3+-ions in ZnO is debated and was thus of particular interest. DFT showed that the dopant Eu was present as 4-8 Eu atom sized oxide clusters distributed within the ZnO at 600 oC. This was also in excellent agreement with the EXAFS, and the other experimental techniques. These structures were highly unexpected, and may help in the understanding of doped oxides. |