Structure Peculiarities of Micro- and Nanocrystalline Perovskite Ferrites La1-x Sm x FeO3.

Micro- and nanocrystalline lanthanum-samarium ferrites La1-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 La1-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 La1-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 La1-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 La1-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.