Abstract: The phase development in the calcination of the precursors for the pseudo-binary system of PFN-PMN was investigated systematically by XRD method. During the
calcination of Mg-rich mixtures, a kind of Mg-rich niobate, Mg₄Nb₂O₉ forms along with the major phase MgNb₂O₆ (MN), whereas in the
calcination of Fe-rich mixture, there is no Mg₄Nb₂O₉ formed, indicating Fe₂O₃ (or FeNbO₄) may inhibit the formation of
Mg₄Nb₂O₉. The appearance of Mg₄Nb₂O₉ is directly related to the formation of pyrochlore in the calcinations of perovskite. MN starts to form at a temperature as
low as 650℃, a temperature much lower than its ferric counterpart FN. Therefore the reactivity of Fe₂O₃ is inferior to that of MgO in
the low temperature region.

Key words: precursor, calcination, MgNb₂O₆, FeNbO₄, perovskite