Relationship between the evaporation of components and microstructure in Pr-doped ZnO ceramics

The change of microstructure and content of components with distance from the surface into the bulk was analyzed for Pr-doped ZnO ceramics as a function of sintering temperature and atmosphere, Pr was segregated at the grain boundary, however, the content was drastically changed by the sintering temperature and atmosphere, Below the liquid phase formation temperature (1350 degrees C), Pr content was constant from the surface into the bulk for the sample sintered in O-2, and Pr content was large at the surface region (0-50 pm) for the sample sintered in N-2. On the other hand, above the liquid phase formation temperature (1500 degrees C), Pr content was lowered at the region between 0 and 300 mu m from the surface for the sample sintered in O-2, and Pr content was large at the surface region (0-50 mu m) for the sample sintered in N-2. This depth profile agreed well with the fraction of grain boundary area, The driving force to cause such Pr content change was ascribed to the increase of the vaporization content of Pr-oxide and ZnO in the sample.