Germanium And Samarium Co-doped Cerium Oxide Degradation Preparation And Performance Research

The SOFC（Solid Oxide Fuel Cell）is a solid-state device that can directly convert the chemical energy of the fuel into electrical energy.The SOFC has the advantages of high-efficiency energy conversion capability and little negative impact on the environment.SOFC electrolyte can be obtained by doping rare earth and alkaline earth elements in CeO₂and it works stably at medium and low temperatures.However,CeO₂-based materials have poor sintering performance,and Ce⁴⁺is easily reduced to Ce³⁺in a reducing atmosphere above 500℃,resulting in open circuit voltage of the battery decrease and output power decrease.At present,doping CeO₂electrolyte is still the focus of electrolyte research at medium and low temperatures.As an important semiconductor material,germanium oxide is widely used in battery research.The doping of germanium in lithium/sodium solid battery electrolyte is helpful to improve the battery’s electrical performance.On the other hand,germanium ion has a small radius and can be used as dopant to promote sintering.However,no studies have been found on Ge doped SOFC electrolyte,so it is necessary to try it.The SDC（samarium oxide doped cerium oxide）electrolyte was synthesized by five experimental methods,and the electrolyte was prepared by a dry pressing process.The powder and electrolyte were characterized,and the performance of SDC was tested under different methods.The citric acid-glycine method was selected as the synthesis method of the following experiment from the comprehensive process and performance.The citric acid-glycine method has high recovery rate,mild reaction,uniform powder,its grain size is0.37 nm,the successful rate of pressing the green body is high,it is easy to demould,and the electrolyte conductivity is high.Its conductivity at 750℃can reach 0.033 S cm^-1.The Ge_xCe_0.8-xSm_0.2O_1.9electrolyte（x=0,0.5%,1%,2%,4%,）was synthesized by the citric acid-glycine method to obtain a fluorite structure solid solution.When the doping amount is 4%,the second phase Sm₂Ge₂O₇is produced.The addition of Ge⁴⁺can cause the diffraction peak to shift to a large Angle,resulting in lattice contraction.Compared with SDC,the doping of Ge accelerates the sintering process and makes the density of GSDC electrolyte increase significantly.The relative density of 1GSDC sintered at 1450℃can reach 99.30%.The thermal expansion coefficient of GSDC electrolyte is similar,and the thermal expansion coefficient of the 1GSDC material is 12.73×10^-6（1/℃）during the heating process of 500～800℃,which matches the thermal expansion coefficient of the electrode material.The doping of Ge eliminates the pores in the material and is conducive to the migration of oxygen ions,thus reducing the grain boundary resistance.The total resistance of the electrolyte sample gradually decreases,and reaches the minimum when the doping amount reaches 1%.The conductivity of the electrolyte sample reaches 0.050 S cm^-1at 750℃.Under the same working temperature,comparing with the SDC,the single cell with 1GSDC as the electrolyte has better power output performance,reaching 552mW/cm²at 750℃,and the power density is increased by 30%.The addition of Ge improves the overall mechanical properties of SDC.1GSDC material is used as a solid electrolyte,which has better mechanical properties than SDC.The Ge_0.01Ce_0.99-xSm_xO_2-δsolid electrolyte（x=10%,20%,30%）was synthesized by the sol-gel method.In the X-ray diffraction pattern,only the diffraction peak corresponding to a single CeO₂cubic fluorite structure exists,With the increase of x,the position of the diffraction peak moves slightly to the low angle direction,and the lattice constant increases,and the lattice expands.The oxygen vacancy and the lattice distortion increases with the increase of Sm³⁺ions,accelerating the sintering process,and makes the density of the Ge_0.01Ce_0.99-xSm_xO_2-δelectrolyte reach more than 95%.he conductivity of Ge_0.01Ce_0.99-xSm_xO_2-δelectrolyte showed the same change rule.With the increase of temperature,the conductivity gradually increased.With the increase of doping amount of Sm³⁺,the conductivity showed a trend of first increasing and then decreasing.the Ge_0.01Ce_0.99-xSm_xO_2-δelectrolyte sintered at 1450℃has the largest conductivity and the conductive activation energy is 0.66 e V.