Phase transformation and microstructure evolution during the sintering of bismuth-manganese chemically doped zinc oxide powders

Chemical preparation of doped powders aims to improve sintering of varistors as well as their dopant distribution, and thus their electrical characteristics. Using Bi-Mn chemically doped ZnO powders with a spherical morphology, we characterize the dopant distribution in powders. Then we analyze the doping effect on the physico-chemistry of sintering. Thus, we identify several Bi or Mn-rich minority phases which crystallize, melt or are dissolved during sintering. These transformations limit or enhance the homogeneity of the Mn distribution in the ceramics.