OXIDATION-STATES OF FE IN LANI1-XFEXO3

The distributoin of oxidation states in perovskites of the type LaA(1- x)B(x)O(3) (A and B transition metal ions) can be ''tailored'' by x va riation. In particular, in LaNiO3 it has been shown that Fe substituti on for Ni feces some Ni3+ into Ni2+, while some Fe3+ changes into the unusual Fe4+ state. In addition, the existence of mixed oxidation stat es of Fe and/or Ni in LaNi1-x,FexO3 has been related to its catalytic activity in hydrogen peroxide decomposition. The Fe4+ population, obta ined using Mossbauer spectroscopy, was found to be constant for all th e analyzed annealing temperatures for x = 0.25 concentration, where th e isomer shift difference for both states is the highest and the catal ytic activity is maximum.