Grain growth in Mn-doped ZnO

Grain growth in ZnO doped with 0.1 to 1.2 mol% Mn was investigated during isothermal sintering from 1100 to 1300°C in air. Mn doping promotes the grain growth of ZnO during sintering, and this effect is enhanced by increasing the Mn doping level. The grain growth exponent is reduced from 3.4, for undoped ZnO, to 2.4, for ZnO doped with 1.2 mol% Mn, while the apparent activation energy for grain growth is reduced from 200 kJ/mol, for undoped ZnO, to 100–150 kJ/mol, for Mn-doped ZnO. Electrical measurements suggest that an excess of Mn probably exists at grain boundaries, either as a very thin second phase or as an amorphous film, which could benefit grain boundary diffusion, therefore promoting the grain growth of ZnO.