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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 15, Number 8
BKCSDE 15(8)
August 20, 1994 

Study of the Nonstoichiometry and Physical Properties of the Nd1-xSrxFeO3-y System
Chul Hyun Yo*, Hyung Rak Kim, Kwang Hyun Ryu, Kwon Sun Roh, Jin Ho Choy
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 have been prepared at 1150℃ in the air pressure. The compound of x=0.00, NdFeO3.0, contains only Fe3+ ion in octahedral site and the others involves the mixed valence state between Fe3+ and Fe4+ ions. The mole ratio of Fe4+ ion or the τ-value increases steadily with the x-value and then is maximized at the compositionof x= 1.00. The nonstoichiometric chemical formulas of the system are formulated from the x, τ and y values. From the Mossbauer spectroscopy, the isomer shift of Fe3+ ion decreases with the increasing x-value, which is induced by the electron transfer between the Fe3+ and Fe4+ ions. The transfer is made possible by the indirect interaction between Fe3+ and Fe4+ ions via the oxygen ion. The eg electrons of the Fe3+ ions are delocalized over all the Fe ions. Due to the electron transfer, the activation energy of electrical conductivity is decrease with the increasing amount of Fe4+ ion.
636 - 640
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