Preparation And Properties Of Apatite-type La_9.33Si_6-xGe_xO₂₆ And La₉A(SiO₄)₆O_2.5 (A=Ca, Sr, Ba) Electrolyte Materials

Solid oxide fuel cell (SOFC) is one of the most clean, efficient energy conversion technology. It can make the chemical energy directly into electricity. The traditional SOFC generally operated at high temperature,but high operating temperature may cause complex issues, such as the interface reaction between the material of electrode sintering and electrolyte and electrode materials。So eager to develop in the temperature area of 600℃to 800℃SOFC operation. The main requirement of developing the IF-SOFC operation is preparation out temperature solid electrolyte materials.In this study, the apatite La_9.33Si_6-xGe_xO₂₆(0≤x≤4) were synthesized with a solid-state method and evaluated it properties by XRD, type electrolyte, conductivity, thermal expansion coefficients ,SEM and the Raman spectra.XRD show that La_9.33Si_6-xGe_xO₂₆ (0≤x≤4) is apatite . With the increasing of Ge, the crystal cell parameters increased send density also increase gradually. Conductivity test showed that, with the increase of Ge content, the conductivity of La_9.33Si_6-xGe_xO₂₆(0≤x≤4) is growing, when x = 4 electric conductivity reach 0.0086 S/cm. When x =4 , the structure changed. It indicate that when Ge: Si = 4:2 , more O (5) appeared. According to the conductive mechanism of apatite, the increasing of O (5) enhance the material conductive properties.This paper also prepared the La₉A(SiO₄)₆O_2.5(A=Ca,Sr,Ba) series of samples by solid phase synthesis method. XRD test results show that La₉A(SiO₄)₆O_2.5(A=Ca,Sr,Ba)is apatite, including Ba doped samples which didn't get single-phase substance because of solid solution is restricted, but it doesn't matter. Through calculation, La₉A(SiO₄)₆O_2.5(A=Ca,Sr,Ba) crystal cell parameters and send density increase with the atomic radius of alkali metal elements increases. Conductivity test showed that, with the increase of alkali metal elements of atom radius increased La₉A(SiO₄)₆O_2.5(A=Ca,Sr,Ba) of electrical conductivity is getting higher and La₉A(SiO₄)₆O_2.5 doped substances in 850℃is 5 maximum of conductivity 0.01 S/cm. Thermal expansion coefficient of samples didn't change.Above all, oxy-apatite are very suitable for doing type electrolyte temperature solid oxide fuel cell electrolytes.