MICROSTRUCTURAL VARIATIONS AS A FUNCTION OF GAMMA IN LA2-XSRXNIO4+GAMMA

A microstructural characterization of the La2-xSrxNiO4+delta (0 less-t han-or-equal-to X less-than-or-equal-to 1) system, prepared with accur ate control of the oxygen content, has been performed. The electron di ffraction study shows the evolution of the accommodation of compositio nal variations as a function of delta. For delta > 0.06, interstitial oxygens are ordered, leading to new K2NiF4 superstructural types. Samp les with delta < 0.06 accommodate the nonstoichiometry by means of ran dom distribution of anionic vacancies.