Effect Of Addition Of Alumina On Microstructure And Mechanical Properties Of LSGM

Sr- and Mg-doped lanthanum gallate(LSGM) first synthesized by Ishihara and Goodenough appears high oxygen ionic conductivity, which has been widely investigated by many scientists. The results show that Sr- and Mg-doped LaGaO₃ was one of the most promising electrolyte candidates for intermediate-temperature solid oxide fuel cells because of its high and exclusive oxygen ionic conductivity at 873-1073K and excellent stability over a broad range of oxygen partial pressure. But the weak mechanical properties of these LaGaO3 -based materials limited their practical application. As was pointed out in Isamu Yasuda's paper, the mechanical strength has been greatly improved without deleteriously affecting conductivity by dispersing 2wt% alumina into the matrix of LSGM. Then in this work, the effects of alumina with different particulate size dispersion on mechanical properties were investigated.In this work, the powder of Sr- and Mg-doped LaGaO₃ material was prepared by conventional solid state reactive firing, alumina with 7μm and 200nm was dispersed respectively. Room-temperature X-ray diffractometry was performed on the sintered samples , the surface and fracture surface of specimen were observed by SEM. Fracture strength , fracture toughness and hardness were researched.The phase structure of three materials were two-phase region, cubic-perovskite and LaSrGa₃O₇, determined from XRD. The weight ratio of LaSrGa₃O₇ increases a little with the alumina dispersion. Alumina was dissolved into crystal lattice of LSGM. The grain size of electrolyte material dispersed with sub-micron alumina was minimum, the value of material dispersed with micron alumina was medial and the grain size of material without alumina was maximum.