Structure Peculiarities of Micro- and Nanocrystalline Perovskite Ferrites La_1-x Sm _x FeO₃

Micro- and nanocrystalline lanthanum-samarium ferrites La_1-x Sm _x FeO₃ with orthorhombic perovskite structure were obtained by using both solid state reactions (x = 0.2, 0.4, 0.6 and 0.8) and sol-gel synthesis (x = 0.5) techniques. Obtained structural parameters of both series of La_1-x Sm _x FeO₃ are in excellent agreement with the "pure" LaFeO₃ and SmFeO₃ compounds, thus proving formation of continuous solid solution in the LaFeO₃-SmFeO₃ system. Peculiarity of La_1-x Sm _x FeO₃ solid solution is divergence behaviour of unit cell dimensions with increasing x: systematic decrease of the a and c lattice parameters is accompanied with increasing b parameter. Such behaviour of the unit cell dimensions in La_1-x Sm _x FeO₃ series led to crossover of the a and c perovskite lattice parameters and formation of dimensionally tetragonal structure near x = 0.04. Linear decrease of the unit cell volume of La_1-x Sm _x FeO₃ with decreasing x according with the Vegard's rule indicate absence of short-range ordering of R-cations in the LaFeO₃-SmFeO₃ system.