New ferroelectric and relaxor ceramics in the mixed oxide system NaNbO3-BaSnO3

New ferroelectric or relaxor ceramics were elaborated in the system Ba1-xNaxSn1-xNbxO3 (BSNN) by solid-state reaction technique. The effect of cationic substitution of barium for sodium in the A sites and tin for niobium in the B sites in the NaNbO3 perovskite lattice on symmetry and physical properties were investigated. Room temperature X-ray diffraction and dielectric permittivity in the temperature range from 80 to 600 K with frequencies from 0.1 to 200 kHz, respectively, were used. The material is relaxor with cubic symmetry when x < 0.90 and becomes classical ferroelectric with a tetragonal cell when 0.90 less than or equal to x < 1. Both T-C or T-m and the maximum of epsilon(T)(1) decrease when BaSnO3 is introduced in the lattice of NaNbO3. The plot of T-m(f)/T-m (1 kHz) versus the logarithm of the frequency allows to determine the limit of composition between the ferroelectric and the relaxor state. Relaxor materials have been obtained at room temperature. (C) 2004 Elsevier SAS. All rights reserved.