Microstructure and properties of ion conductors in the ZrO2-Y2O3-MgO system as an effect of DIGM process

Paper contains results of microstructure and chemical composition analyses of micrograins which formed on initial grain boundaries in three systems: Z rO2 + 5 mol.% Y2O3, ZrO2 + + 6 mol.% Y2O3 and ZrO2 + 6 mol.% Y2O3 + 5.4 mol .% MgO. It was found out that the micrograins appeared in the process of di ffusion induced grain boundary migration (DIGM). They revealed an increased level of Y2O3 content (up to 2 mol.%) and a cubic symmetry. DIGM investiga tions were conducted after a heat-treatment of the samples at 1500 degrees C for 50 hours and at 1700 degrees C for 2 hours. Zirconia - yttria solid s olution with magnesia particulate addition showed the increase of amount of migration nuclei and the size of new-created grains. However, no change in the chemical composition of the grains was detected. The mechanical properties and ion conductivity of the material were investi gated. It was established that the ZrO2 + 6 mol.% Y2O3 ceramic showed the h ighest grain boundary conductivity and highest (sigma(gb)/sigma(tot)) ratio of all the investigated system, This material has high hardness and slight ly decreased fracture toughness. It seems to be a perspective material for solid electrolytes.