Study of the structural and electrical properties of some mixed valence perovskite systems.

Mixed valence perovskite systems exhibit interesting physical properties. Though a number of mixed valance systems have been reported and studied, there seems to have been no studies on the realization of 2+ and 3+ oxidation states of Mn, Co or Fe, by doping at the A sites of the perovskite structure. Hence the following systems have been prepared by solid-state sintering methods starting from the oxides or carbonates of the constituent elements and studied in this work. I Ba 1-x Nax(Mn 1/3 Nb 2/3 )O3 For 0 < x < 0.33 II Ba 1-x Nax(Co 1/3 Nb 2/3 )O3 For 0 < x < 0.33 III Ba 1-x Lax(Fe 1/3 Nb 1/2 )O3 For 0 < x < 0.30. The samples were characterized by x-ray diffraction, electron spin resonance, scanning electron microscopy, infra-red absorption, laser Raman spectra and Mossbauer spectra (system III only). The electrical properties studied include Seebeck coefficient, d.c. conductivity and impedance spectra. More Info

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Tue, 28/09/2010 - 18:42