Nonisothermal sintering of Mn doped ZnO

Abstract

The sintering of pure ZnO and ZnO doped with Mn, obtained by addition of Mn(NO 3) 2. 4H 2O in the concentration from 0·1 to 1·2 mol%, was investigated by dilatometry at constant heating rates, from 1 to 15 °C min −1. Mn shifts the onset of the sintering towards higher temperatures, but no significant effect of the Mn doping level on the shrinkage was observed. Accordingly, the calculated activation energy for the first stage, changed from ∼320 kJ mol −1 for pure ZnO to ∼440 kJ mol −1 for Mn doped ZnO. Using classical sintering models to analyse the initial stage sintering of all the compositions, two sintering mechanisms were found to control the initial stage sintering. The first region is identified with a grain boundary sliding mechanism, while volume diffusion is the controlling mechanism in the second region. With the increase of the Mn content, the grain boundary sliding rate remains constant, but the volume diffusion rate is reduced.