Grain boundaryʹs conductivity in heavily yttrium doped ceria

Four high purity heavily yttrium doped ceria (YDC, YxCe1 − xO2 − δ, x = 0.1, 0.15, 0.2 0.25) electrolytes were prepared and their grain boundaries (GBs) were investigated by impedance spectroscopy (IS) and transmission electron microscopy (TEM). IS data indicated that single GBʹs resistance and GBʹs thickness firstly decreased and then increased with increasing doping level. TEM investigation on GBs suggested the formation of nanodomains at GBs was responsible for the increase of GBʹs electrical thickness. Our work suggests in heavy doping level ceria, in addition to the space charge effect, nanodomainʹs blocking effect is another contribution to the high GB resistivity. According to the microstructure evolution of YDC with increasing doping level, we suggest three factors that influence nanodomainʹs segregation to GBs.