Preparation And Characterization Of Doped Ceria/Lanthanum Silicate Composite Electrolyte

The solid oxide fuel cell?abbreviated SOFC?can convert chemical energy into electric energy directly.It has attracted much attention due to its clean,pollution-free and high working efficiency.Serve as core components of fuel cells,the electrolytes should exhibit excellent transport ability,bonding ability with anode/cathode,but also good mechanical properties.So as to the cracking caused by thermal stress during preparation and operation can be avoided.In this research,samarium and neodymium co-doped ceria?SNDC?with fluorite structure and apatite-type lanthanum silicate?LSO?composites were prepared,and their electrical and mechanical properties were investigated.The samarium and neodymium co-doped ceria(Sm_0.1Nd_0.1Ce_0.8O_2-?,abbreviated SNDC)powders were prepared by glycine-nitrate combustion method.The lanthanum silicate(La₁₀Si₆O₂₇,abbreviated LSO)powders were obtained by sol-gel method.The LSO powders were added to the SNDC matrix at different mass ratios?0:100,3:97,5:95,10:90,20:80,30:70,50:50,100:0?.The mixed powders after milling were sintered at different temperature,and dense bulks were obtained.In order to analyze the impact of sintering temperature and LSO content on grain/grain boundary/total conductivities of the samples,the electrochemical impedance spectroscopy?EIS?measurements were carried out.The results shows that the samples sintered at 1600?exhibit highest conductivity,and the addition of LSO decreased the grain boundary conductivity effectively.When the LSO content is 5wt%,the conductivity of composite is higher than SNDC by5%.The fracture toughness and flexural strength of the samples were tested by indentation and three-point bending respectively,and their relationship with LSO addition was analyzed.It was found that the fracture toughness achieved25%increase compared with the pure compound with 5wt%LSO content.And about 7wt%LSO lanthanum silicate added into Sm and Nd co-doped ceria,the flexural strength reach to as high as 242±48 MPa,which is 71%enhancement to pure SNDC.Considering the synergetic improvement of mechanical and electrical properties,the SNDC/LSO composite electrolytes may be a promising candidate material in intermediate temperature SOFCs.