Local Structural Evolution of Co-Doped ZnO Nanoparticles upon Calcination Studied by in Situ Quick-Scan XAFS

Co-doped ZnO is a good dilute ferromagnetic semiconductor candidate with high Curie temperature. In this work, Zn0.93Co0.07O nanoparticles of about 5 nm in size were synthesized by the coprecipitation method. X-ray absorption fine structure spectra at both Co and Zn K-edges were acquired at an in situ and quick-scan mode while the sample was heated to 730 °C in air. The results show a good incorporation of cobalt ions into substitutional zinc sites in zinc oxide. Upon calcination, a systematic structural variation can be monitored, from removal of hydroxyl groups to cobalt oxide precipitation. The Einstein temperature, estimated from the Debye−Waller factor−temperature plot, indicates a stronger Co−ligand bond strength in the lattice compared to that of the ZnO matrix.