添加Li_2O对YSZ电解质性能影响

8%（摩尔分数,下同）Y2O3稳定的ZrO2（8YSZ）是固体氧化物燃料电池（SOFC）中最常用的电解质材料,本文研究了在8YSZ基体中加入n%Li2O（n=0,0.25,0.50,1.00,1.50,1.70,2.00,2.50,3.00）后（记为n%Li2OYSZ）对其晶相结构、晶格常数、烧结性能、微观形貌、电导率及其作为SOFC电解质性能的影响。结果表明,Li2O中的Li＋可以固溶到YSZ的晶格内使其晶格常数减小;Li2O的加入量n〈1.70时,瓷体在烧结过程中不会发生相变。加入少量的Li2O（n=0.25,0.50）可以提高YSZ的致密度和电导率,0.25%Li2OYSZ和0.50%Li2OYSZ样品800℃的电导率分别高达0.030 2 S/cm和0.027 6 S/cm,分别是纯YSZ的1.35和1.24倍;当Li2O含量n≥1.00时,相同条件下烧结体致密度随Li2O加入量的增大而逐渐减小;当n≥1.70时,样品在烧结过程中虽然出现相变,但在高于1400℃可以烧结致密,并得到纯立方相YSZ。将1250℃烧结制得的0.25%Li2OYSZ和0.50%Li2OYSZ作为SOFC电解质的单电池,800℃时的开路电压高于1.0V,说明YSZ中没有出现电子电导,具有比纯YSZ为电解质的单电池更高的性能输出,表现出了良好的应用前景。

Properties of Yttria Doped Zirconia Electrolyte with Li2O Additive

The zirconia doped with yttria of 8%(mole fraction,the same below)(8YSZ) is a widely used electrolyte in solid oxide fuel cells(SOFCs).The crystal structure,lattice parameter,sintering ability,microstructure,conductivity and cell performance of 8YSZ with various Li2O contents(i.e.,n% of Li2OYSZ,where n = 0,0.25,0.50,1.00,1.50,1.70,2.00,2.50 and 3.00) were investigated.The results show that the lithium ions can dissolve into the ZrO2cubic lattice and reduce its lattice parameter due to small radius of lithium ions.The YSZ remained its cubic lattice until Li2O addition of 1.70%.Li2O addition of 0.25% and 0.50% enhanced both the density and electrical conductivity of the YSZ samples.The conductivities obtained at Li2OYSZ of 0.25% and 0.50% and 800 ℃ were 0.030 2 S/cm and 0.027 6 S/cm,which were 1.35 and 1.24 times greater than that of pure YSZ,respectively.The density of the YSZ samples reduced gradually when the Li2O addition was greater than 1.00%.The dense ceramic with the pure cubic phase could be obtained at sintering temperature of > 1 400 ℃ and Li2OYSZ of ≥1.70%.The SOFCs with Li2OYSZ of 0.25% and 0.50% electrolyte displayed open circuit voltages of > 1.0 V at 800 ℃,indicating the absence of electronic conductivity,and exhibiting the maximum power densities that are greater than those of the cell with pure YSZ electrolyte.It was demonstrated that a small amount of Li2O addition into YSZ electrolyte could be a desirable modification approach for zirconia-based SOFC.