Rietveld refinement of transition metal doped ZnO

Nanocrystals of Zn 1−x M x O ( M =Mn, Co, or Ni) were grown using proteic sol-gel process, and the crystalline phases were identified by X-ray diffraction and Rietveld refinement. The nanocrystals have hexagonal wurtzite structure, with space group P 63 mc . The insertion of Mn 2+ in the place of Zn 2+ provoked an increase in the size of the nanocrystals, and the insertion of Co 2+ or Ni 2+ caused a reduction in the sizes of the nanocrystals, as compared to pure ZnO. This occurred because these three transition metals have very different ionic radii (Co 2+ =0.58 A˚, Mn 2+ =0.66 A˚, Ni 2+ =0.55 A˚, and Zn 2+ =0.60 A˚).