Effect of Bi and Ti substitutions for Na and Nb on ferroelectric properties of oriented (Bi_(4.5+x)Na_(0.5-x))(Ti_(2x)Nb_(2-2x)WO_(15) compounds

摘要

(Bi_(4.5+x)Na_(0.5-x))(Ti_(2x)Nb_(2-2x)WO_(15)(BNTNW) compounds were synthesized and their ferroelectric properties were characterized. The X-ray powder diffraction patterns of the compounds revealed that they have a single phase over the whole composition range. The linear variations of the lattice parameters with composition indicate the formation of solid solutions, resulting in a reduction in the orthorhombicity of the compounds. The remnant polarization of the BNTNW decreased from 8.5 to 5.1 μC/cm~2 with increasing x, which may be related to the orthorhombicity of the compounds. By using hot forging, an oriented BNTNW compound at x - 0 was obtained. Strong reflections from (0 01) were observed for sample // in which the measurement direction is parallel and the orientation factor of such sample was approximately 0.72. A remarkable increase in the remnant polarization (P_r) of the compound was observed for the sample ⊥ in which the direction of applied pressure is perpendicular to the measurement direction; the highest P_r value was 18 μC/cm~2.