STUDY OF THE NONSTOICHIOMETRY AND PHYSICAL-PROPERTIES OF THE ND1-XSRXFEOS3-Y SYSTEM

The nonstoichiometric perovskite solid solutions of the Nd1-xSrxFeO3-y system for the compositions of x=0.00, 0.25, 0.50, 0.75, and 1.00 hav e been prepared at 1150 degrees C in the air pressure. The compound of x=0.00, NdFeO30, contains only Fe3+ ion in octahedral site and the ot hers involves the mixed valence state between Fe3+ and Fe4+ ions. The mole ratio of Fe4+ ion or the tau-value increases steadily with the x- value and then is maximized at the composition of x=1.00. The nonstoic hiometric chemical formulas of the system are formulated from the x, t au, and y values. From the Mossbauer spectroscopy, the isomer shift of Fe3+ ion decreases with the increasing x-value, which is induced by t he electron transfer between the Fe3+ and Fe4+ ions. The transfer is m ade possible by the indirect interaction between Fe3+ and Fe4+ ions vi a the oxygen ion. The e(g) electrons of the Fe3+ ions are delocalized over all the Fe ions. Due to the electron transfer, the activation ene rgy of electrical conductivity is decrease with the increasing amount of Fe4+ ion.