Preparation, Structural and Electrophysical Studies of Ferroelectric Ceramic Samples of the System (1-2x)BiScO3-xPbTiO3-xPbMg1/3Nb2/3O3, 0 ≤ x ≤ 0.50

Abstract

Ceramic samples of the (1-2x)BiScO3-xPbTiO3-xPbMg1/3Nb2/3O3 system in the whole compositions region x = 0-0.50 were synthesized. According to the X-ray diffraction studies (XRD), the region of solid solutions with perovskite structure formation in the system was determined (x = 0.23-0.50). The presence of a morphotropic phase boundary between tetragonal and rhombohedral forms of solid solutions was established at x = 0.40-0.42. Refined XRD with profile peak analysis established the presence of the additional cubic phase with broadened X-ray reflexes in the solid solutions along with the main phase. It was concluded that the main and additional phases are located in the volume and in the surface layer of ceramic crystallites, respectively. The crystal structures of phases in the polarized and depolarized sample with x = 0.42 were determined by the Rietveld method. It was found that the monoclinic perovskite phase is present in the polarized sample. Temperature-frequency dependences of dielectric permittivity and losses of solid solutions were studied. It was found that the increasing content of BiScO3 in samples causes a change in their dielectric properties from the usual ferroelectric (FE) in the region (1-2x) = 0-0.08 to ferroelectric-relaxor (FE-R) in the region (1-2x) = 0.08-0.40, and then to the properties of dipole glass with weak correlations in the region (1-2x) > 0.40. It was found that the samples with x = 0.434 and 0.446 below Tc = 414 and 445 K spontaneously pass to the FE state. In the samples with x = 0.42 the application of an electric field of 2.0 kV/ cm induces a transition from FE-R to FE state with Tc = 350 K, which remains after the field is removed.

Keywords

• ferroelectric ceramics
• ferroelectrics
• relaxors
• solid solutions
• crystal structure
• dielectric properties