Investigation of valence states in the perovskite oxides, LaAFeNbO<inf>6</inf> (A = Ca, Sr)

Compounds of the type, LaAFeNbO6 (A = Ca, Sr) have been synthesized to study the electrical and magnetic properties and to examine valence degeneracy. The results show that valence degeneracy is not operative and the compounds are insulating. Magnetic susceptibility data show that part of the Fe is in Fe2+ state, thus oxidizing part of Nb4+ to Nb5+ by an internal redox mechanism. The presence of mixed valent Fe is confirmed by Moessbauer spectra.