Synthesis of AFeO(2.5+x)(0 <= x <= 0.5; A = Sr, Ca) mixed oxides from the oxidative thermal decomposition of A[Fe(CN)(5)NO]center dot 4H(2)O

The ion-temperature formation of Sr and Ca ferrates by thermal oxidative de composition of tetrahydrates of Sr and Ca nitroprussides (pentacyanonitrosi lferrates(II)) is reported. IR spectroscopy, X-ray diffraction (including R ietveld analysis), and thermal analysis were used to follow the process. Th e amount of active oxygen (concentration of Fe(IV)) in the products was che mically determined. For the Sr compound, the final product was an oxygen-de ficient perovskite that could be produced with a very low content of carbon ate in the temperature range 750-850 degrees C. For the calcium compound, o nly Ca2Fe2O5 with the brownmillerite type structure was obtained. (C) 1999 Academic Press.