Nonstoichiometry and physical properties of the two dimensional Sr{sub 1+x}Nd{sub 1-x}FeO{sub 4-y} system
- Yonsei Univ., Seoul (Korea, Democratic People`s Republic of)
The compounds Sr{sub 1+x}Nd{sub 1-x}FeO{sub 4-y}(x=0.00,0.25,0.50,0.75, and 1.00) with the K{sub 2}NiF{sub 4} structure are prepared by a drip pyrolysis technique. X-ray powder diffraction analysis assigns all the compositions to the tetragonal system with decreasing lattice volume as x increases. Nonstoichiometric chemical formulas are formulated and identified by Mohr salt analysis and Moessbauer spectroscopy, respectively. Oxygen vacancy formation is predominant rather than the oxidation of the Fe{sup 3+} ion to the Fe{sup 4+} ion with respect to the competitive compensation for the positive charge deficiency. The electrical and magnetic properties of these compounds, with the space group I4/mmm, are different from those of the corresponding three-dimensional perovskites. All the compositions of the two-dimensional Sr{sub 1+x}Nd{sub 1-x}FeO{sub 4-y} compounds are within the semiconducting range with positive temperature dependence of the electrical conductivity. Although the amount of Fe{sup 4+} ion is maximum at the composition of x = 1.00, its lowest electrical conductivity can be associated, not with the conduction carrier concentration, but with the mobility which depends on the amount of the oxygen vacancy and on the Fe-O-Fe bond distance. As a result of the magnetic measurement with a SQUID, all the compositions follow the Curie-Weiss law and the anomalous effective magnetic moments of the compositions can be interpreted as a coexistence of low and high spins of the mixed valence state.
- OSTI ID:
- 274262
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 123; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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