Co-doping Effect on Microstructures and Ionic Conductivity of Aliovalent Cations Modified Ceria

Microstructural features and ionic conductivity of divalent(Mg 2+)and trivalent(Gd 3+)cations co-doped ceria electrolyte system Ce_ 0.8-xGd_ 0.2Mg_xO_ 1.9-x were investigated by scanning electron microscopy(SEM)and AC impedance analysis.The experimental results exhibit that addition of MgO to GDC reduces the average binding energy of GDC by decreasing the energy barrier of oxygen ion migration in ceria matrix and the ionic conductivity of 2 mol% magnesium doped GDC(0.018 S/cm)is higher than that of GDC matrix at 650℃(0.0105 S/cm).Co-doping Mg 2+ and Gd 3+ is found to increase the ionic conductivity of ceria and hence decreases the operation temperature as well as the cost of solid oxide fuel cell(SOFC).

Electrical Properties and Grain Growth Kinetics of PZN-based Ceramics Using Microwave Sintering

Effectiveness of microwave sintering process through investigation of microstructural characteristics and electrical properties of x(0.94PbZn_ 1/3Nb_ 2/3O_3 + 0.06BaTiO_3)+(1-x)PbZr_yTi_ 1-yO_3(PBZNZT)ceramics with x=0.6 and y=0.52 was evaluated.The relative density of 95% was achieved with sintering at 800℃ for 2 h.The small grain growth exponents indicate how easy the grain growth in these materials sintered using microwave radiation.Grain growth rate increases abruptly and is higher than that of conventional sintering at a temperature higher than 1050℃.This is attributed to the lower activation energy and higher grain boundary mobility.The activation energy required for the grain growth is found to be 132kJ/mol.Higher remanent polarization(Pr=50.1μC/cm2)and increase in remanent polarization with sintering temperature are observed in microwave sintering process when compared to that of conventional sintering process,due to fast increase in grain growth rate and homogeneity in the specimen.The results indicate lower sintering energy and reduction of PbO pollution in the working environment by microwave sintering process.