Nonstoichiometry and electrical properties of the perovskite

摘要

phase4 formation studies in the system Ca_2Fe_2-xNb_xO_γ indicated the presence of a cubic solid solution for 0.45 ≤x≤0.65, which has variable oxygen content with an oxygen-deficient perovskite structure. As synthesised, for x=0.6 it contains a mixture of Fe~4+ and Fe~3+ in the ratio 13/87. The oxygen content was modified by heat treatments under various atmospheres over the range 5.5.≤γ≤5.92 which corresponded to the ratios: 93/7 to Fe~3+Fe~2+ and 42/58 of Fe~4+/Fe~3+, respectively.