Optimization of Sol–Gel-Formed ZnO:Al Processing Parameters by Observation of Dopant Ion Location Using Solid-State <sup>27</sup>Al NMR Spectrometry Tim Kemmitt Bridget Ingham Rachael Linklater 10.1021/jp204283k.s001 https://acs.figshare.com/articles/journal_contribution/Optimization_of_Sol_Gel_Formed_ZnO_Al_Processing_Parameters_by_Observation_of_Dopant_Ion_Location_Using_Solid_State_sup_27_sup_Al_NMR_Spectrometry/2626466 We report the discrimination of Al doping sites in sol–gel-formed ZnO powders by solid-state <sup>27</sup>Al nuclear magnetic resonance (NMR) spectrometry. A degree of control of dopant placement is demonstrated by modifying sol precursors and processing parameters. ZnO powders containing 1–8 at. % aluminum ions were prepared from aqueous citrate-amino-alcohol-based gels calcined at 500 °C. The powders were characterized using <sup>27</sup>Al NMR spectrometry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Solid-state <sup>27</sup>Al NMR spectrometry clearly distinguished between different Al environments and was effective in determining the relative amounts of incorporation of Al dopant ions into the Zn lattice sites in the zincite structure. This allowed a synthesis protocol to be developed to optimize the doping effectiveness. Relatively minor variations in processing conditions could influence the degree and mode of Al incorporation. Optimal conditions were found to include a 90 °C drying step, followed by placement in a preheated (500 °C) furnace for 1 h. An ethanolamine-containing precursor was shown to perform much better than precursors containing alternative amino alcohols. 2011-08-04 00:00:00 Al dopant ions synthesis protocol Al environments Al doping sites sol precursors zincite structure 27 Al XRD Dopant Ion Location Zn lattice sites processing conditions dopant placement SEM ZnO powders scanning electron microscopy 1 h Al incorporation 27 Al NMR spectrometry Optimal conditions doping effectiveness processing parameters