La2-xSrxNiO4体系还原性能考察及La1.7Sr0.3NiO4还原机理的研究

合成了四方晶系K_2NiF_4结构的La_(2-x)Sr_xNiO_4(0.0≤x≤1.0)系列复合氧化物。用多晶XRD技术测定其晶胞参数; 用程序升温还原(TPR)技术研究了它们的还原性能。结果发现系列样品的最高还原峰温随组成(x)的变化次序和晶胞参数a的变化次序相反, 而与c的变化次序相同。利用TPR和XRD技术考察了La_(1.7)Sr_(0.3)NiO_4的还原机理, 发现此样品TPR图中前两个还原峰主要对应于Ni~(3+)还原成Ni~(2+)离子的过程, 同时轴比率c/a的计算也间接佐证了这一点; 并将最高还原峰归属于结构的破坏峰。

INVESTIGATION OF THE REDUCIBILITY OF La_(2-x)Sr_xNiO_4 SYSTEM AND THE STUDY OF REDUCIBLE MECHANISM FOR La_(1.7)Sr_(0.3)NiO_4

A series of La_(2-x)Sr_xNiO_4(0.0≤x≤1.0) oxides with the tetragonal K_2NiF_4 structure were prepared. The cell parameters were measured by powder X-ray diffraction (XRD) technique; the reducibility was determined by temperature programmed reduction(TPR). Results show that the changing orders of the highest reducing peak temperature with composition(x) contrast to that of cell parameter a, but agree with that of c. The reducing mechanism for La_(1.7)Sr_(0.3)NiO_4 was investigated by TPR and XRD technique. We found that the first two reducing peaks in TPR profile correspond mainly to the reducing process from Ni~(3+) ion to Ni~(2+). This point was also identified by the calculation of axial ratio indirectly; therefore the highest reducing peak is the structural destroying peak.