Fabrication Of La₁₀Si_5.8Mg_0.2O_26.8 Electrolyte Films And Their Anode Functional Layers

Solid Oxide Fuel Cell?SOFCs?is an energy conversion device for changing chemical energy of the fuel into electricity.SOFCs are not only a clean energy,but also a very efficient energy.Because the traditional SOFCs are running at high temperature which seriously limits the development of SOFCs,low-and intermediate temperature SOFCs has become a research focus at this stage.The low temperature SOFCs reduce the operating temperature,make the performance of SOFCs more stable;longer service life;better compatibility between materials and lower production costs.At the same time,low-temperature SOFCs can also accelerate the start-up speed;reduce the start-up time;enlarge the use of space and promote the commercialization of SOFCs.Therefore,looking electrolyte materials with high ionic conductivity at low-and intermediate temperature and filming of electrolyte have become the key to the study.We selected the new type of oxygen ion conductor apatite-type lanthanum silicate La₁₀Si_5.8Mg_0.2O_26.8 with high ionic conductivity at low-and intermediate temperature as the material for preparing the electrolyte membrane.The ratio of SiO₂ to La₂O₃ in apatite lanthanum silicate is 9 to 7.This material has a relatively low activation energy and a relatively high oxygen anion conductivity.In the wide range of oxygen partial pressures,it is an excellent pure oxygen ion conductor.At the same time,it also has high chemical stability,low coefficient of thermal expansion,and it is a very promising electrolyte material for intermediate temperature SOFCs.In order to obtain a uniform and dense electrolyte film on the porous anode,a Ni / La₁₀Si_5.8Mg_0.2O_26.8 anode functional layer was prepared on a nickel / apatite lanthanum composite anode by screen printing.The Ni O / La₁₀Si_5.8Mg_0.2O_26.8 powder was mixed with terpineol in a mass ratio of 6: 4 and different amounts of ethyl cellulose were added as binders to obtain functional layer slurry.The slurry was printed on an anode substrate with a scraper,dried at 70 °C for half an hour,and then sintered at 1050 °C for 2 h.Finally,the Ni / La₁₀Si_5.8Mg_0.2O_26.8 anode functional layer was prepared by reduction in hydrogen at 600 °C.The phases,surface microstructure of the anode functional layer were characterized by XRD and SEM.The porosity and resistance at room temperature of the samples were determined by image analysis and multimeter.The experimental results show that the anode functional layer prepared with 14wt% ethyl cellulose has no obvious cracks,and the average pore size is below 1?m.When the ethyl cellulose content is very small or very large then the hole size of the functional layer becomes larger and there are cracks.After the sample is reduced,the resistance measured is in the range of 2.0 ? to 2.2 ?.The functional layer obtained by adding 14wt% ethyl cellulose as the binder is the best considering the phase,surface microstructure and resistance of the anode functional layer.In this paper,the magnetron sputtering method was used to prepare the apatite-type La₁₀Si_5.8Mg_0.2O_26.8 electrolyte film.The influences of the preparation of the electrolyte film by magnetron sputtering are discussed in detail.The electrolyte films were characterized by EPMA,SEM and XRD.The optimum parameters for the deposition of La₁₀Si_5.8Mg_0.2O_26.8 electrolyte films by RF magnetron sputtering are working pressure: 0.7 Pa,power supply: 80 W,substrate temperature: room temperature,annealing temperature: 1100°C,annealing Time: 6 h.