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-δ,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.