Z. Kristallogr. Proc. 1 (2011) 75-80 / DOI 10.1524/zkpr.2011.0011 75 © by Oldenbourg Wissenschaftsverlag, München High energy milling of Cu 2 O powders D. Dodoo-Arhin, G. Vettori, M. D’Incau, M. Leoni * , P. Scardi University of Trento, Department of Material Engineering, Trento, Italy * Contact author; e-mail: Matteo.Leoni@unitn.it Keywords: high energy milling, Whole Powder Pattern Modelling Abstract. Whole Powder Pattern Modelling was employed to investigate the microstructure changes in Cu 2 O powders milled in a vibrating cup mill. The reduction in the average size of coherently scattering domains - and simultaneous narrowing of the size distribution - occurs in the first minutes. An asymptotic limit of ca. 10 nm is obtained. The reduction in size is obtained at the expenses of introducing a massive quantity of dislocations in the system, reaching a limit of ca. 4×10 -16 m -2 . A proper nanocrystalline microstructure can be obtained with an effective milling time of ca. 20 min. Introduction Nano-sized particles keep attracting the attention of the scientific community because of their peculiar properties arising both from the high surface/volume ratio and from the possi- ble quantum confinement effects. Several methods have been proposed for the synthesis of nanostructured materials. Among them, high energy milling has an undoubted technological importance as it allows producing large quantities of powder in short time and at competitive prices [1]. The microstructure of the nanostructured materials resulting from milling can be conveniently investigated by microscopy and by X-ray diffraction (XRD). XRD of nanocrys- talline powders guarantees a better statistical significance of the result, as the information is collected on a much larger quantity of grains (millions versus tens analyzed under the micro- scope). Line Profile Analysis (LPA) is the group of techniques employed for microstructure analysis from diffraction data, as they are based on the analysis of the broadening of the diffraction peaks [2]. It should be recalled that the broadening of the X-ray diffraction line profiles is determined by instrumental features but also by the small size of the coherently scattering domains (aka crystallites) and by lattice distortions (dislocations, stacking faults, etc). The most widespread techniques for microstructure analysis based on XRD data are certainly the Scherrer formula [3] and the Williamson-Hall plot [4], that are quite often used without care on the underlying theory or hypotheses, and imposing an arbitrary shape to the peaks. The state of the art alternative is offered by full pattern methods, like, e.g., the Whole Powder Pattern Modelling (WPPM) [5], that provides for an interpretation of the whole dif- fraction pattern in terms of physical models for the broadening sources. Cuprite Cu 2 O is a wide bandgap (2.0–2.2eV) p-type semiconductor that finds important technological applications e.g. in solar cells, gas sensors chemical refinement catalysis and