NONSTOICHIOMETRY AND PHYSICAL-PROPERTIES OF THE PEROVSKITE BAXLA1-XFEO3-Y SYSTEM

A series of samples in the BaxLa1-xFeO3-y system (x = 0.00, 0.25, 0.50 , 0.75, and 1.00) have been prepared at 1200 degrees C under an atmosp heric air pressure. The solid solutions of the system were analysed fr om the X-ray diffraction spectra and thermal analyses. X-ray diffracti on studies assigned the compositions of the x = 0.00 and 1.00 to the o rthorhombic system and the compositions of the x = 0.25, 0.50, and 0.7 5 to the cubic system. The reduced lattice volume increased with the x value in the system. The mole ratios of the Fe4+ ion in the solid sol utions, or tau values, were determined by Mohr salt analyses and the n on-stoichiometric chemical formulae of the system were formulated from the x, tau, and y values. From the results of the Mossbauer spectrosc opy, the coordination and the magnetic property of the iron ion have b een discussed. The electrical conductivities were measured as a functi on of temperature under atmospheric air pressure. The activation energ y was minimum at the composition of x = 0.50. The conduction mechanism can be explained by the hopping model between the mixed valences of t he Fe3+ and Fe4+ ions.