| Abstract Scope |
A solution 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, (S)TEM-ED/EELS/HAADF/ePDF, XPS, and EXAFS. The ZnO:Eu sponges obtained at up to 650 oC showed only peaks of hex-ZnO with unit cell-dimensions very close to pure ZnO. Heating to 700-1000 oC, caused formation of c-Eu2O3 nano-crystals (XRD). DFT calculations of structures with 4.2% Eu in ZnO showed, in excellent agreement with EXAFS and XRD, that the dopant Eu was present as 4-8 Eu atom sized oxide clusters distributed within the ZnO. These structures should only be obtained with <10-15% Eu in order to have Eu-oxide clusters isolated by ZnO, but XRD showed no phase-separation up to 20%Eu. (S)TEM-mapping and ePDF allowed to describe the ZnO:Eu and amorphous inter-crystalline phase obtained with ZnO:20%Eu. |