Dielectric, Ferroelectric, Electromechanical and Impedance Studies on Na 0.5-x K x Bi 0.5-x Dy x TiO 3 Ceramics.

Na0.5-xKxBi0.5-xDyxTiO3ceramics with x = 0.0125, 0.025 and 0.05 were prepared through solid state reaction method. X-ray diffraction studies showed that substitution of K+1and Dy+3ions has not resulted in any change of crystal structure. The SEM graphs indicate the Dy+3doping inhibits the grain growth to some extent. Two abnormal peaks were observed in the temperature dependence of dielectric plots. With the increase of K+1and Dy+3concentrations, the degree of relaxor behaviour and diffusiveness of phase transition is found to increase. Ceramic composition with x = 0.025 exhibits high ferroelectric property with remnant polarization (Pr) around 5.77 μC/cm2and coercive filed (Ec) ∼ 26.22 kV/cm, when compared to other compositions. Lower value of remnant polarization for present ceramic materials when compared to pure sodium bismuth titanate is attributed to domain wall clamping, which restrains the macro-micro domain switching. Impedance studies revealed that rare-earth doping restrained the migration of charge carriers. This is attributed to A site vacancy related phenomena. [ABSTRACT FROM PUBLISHER]