# Synthesis of ZnO by wet chemical method and reducing particle size by ball milling

I synthesized bulk $\ce{ZnO}$ which is pure white in colour, but after high energy ball milling colour changes from white to yellow, why?

Figure 1: Zinc oxide (courtesy of Wikipedia).

• Are you sure it is not contaminated by the balls and mill material? What is the nature of the balls and the mill? – Yomen Atassi Apr 7 '17 at 13:20
• How did you proceed in detail, by "wet method" you refer to what liquid? – Buttonwood Apr 7 '17 at 14:58
• I suspect non-stoichiometry. Zinc oxide turns to $\ce{Zn_{(1+x)}O}$ which is yellow in color. – Nilay Ghosh Aug 1 '17 at 14:18