Oxygen Nonstoichiometry, Crystal Structureand Mechanical Properties of La_2NiO_(4+δ)

摘要

Crystal structure and mechanical properties of La_2NiO_(4+δ) weremeasured by high temperature X-ray diffractometry and in-situsmall punch test as a function of temperature and oxygen partialpressure. As P(O_2) increases, the lattice parameter perpendicular tothe perovskite layer increases and that parallel to the layer slightlydecreases, and the lattice volume slightly increases. Apparent andtrue thermal expansion coefficients were calculated from thevariation of the lattice constants. The elastic modulus and thefracture strength become larger at higher P(O_2) condition. Thismay be caused by the structural change due to excess oxygen.