Structure and dielectric properties of (1−x)Ag0.9Li0.1NbO3–(x)Bi0.5K0.5TiO3 ferroelectric ceramics

New (1−x)Ag0.9Li0.1NbO3–xBi0.5K0.5TiO3 ceramics were synthesized and investigated by means of broadband dielectric spectroscopy (20 Hz–37 GHz), an X-ray and an SEM. It was demonstrated that the ferroelectric phase transition temperature does not monotonically decreases with Bi0.5K0.5TiO3 concentration and the ferroelectric phase transition completely vanishes in 0.85Ag0.9Li0.1NbO3–0.15Bi0.5K0.5TiO3 ceramics, where the relaxor behavior is observed. In contrast the antiferroelectric phase transition disappears in 0.9Ag0.9Li0.1NbO3–0.1Bi0.5K0.5TiO3 ceramics, at room temperature these ceramics are close to a rhombohedral–tetragonal phase boundary. The static dielectric permittivity increases with Bi0.5K0.5TiO3 concentration due to the increase of disorder in the system and gradual appearance of new excitations in the dielectric spectra: a microwave relaxation soft mode and dynamics of polar nanoregions.