Ferroelectric-relaxor behavior of (Na0.5K0.5)NbO3-based ceramics

We report that ferroelectric-relaxor behavior is induced by doping of SrO and TiO₂, or BaO and TiO₂ into classic ferroelectric (Na_0.5K_0.5)NbO₃. It is found that [(Na_0.5K_0.5)_0.9Sr_0.1](Nb_0.9Ti_0.1)O₃ ceramics exhibit a pronounced ferroelectric-relaxor behavior, comparable to that of [(Na_0.5K_0.5)_0.9Ba_0.1](Nb_0.9Ti_0.1)O₃ ceramics. Our results indicate that the relaxor behavior is closely related to the appearance of micropolar regions in these systems. The relaxor behavior should arise from the dynamic response of micropolar clusters. Raman spectra of [(Na_0.5K_0.5)_1−xSr_x](Nb_1−xTi_x)O₃ ceramics measured in the wavenumber range from 100 to 1200 cm⁻¹ confirm that the first order scattering is dominant in phonon bands should result from both short-range ordered region (micropolar regions) and disordered matrix. The frequency dependence of dielectric permittivity measurements show that the relaxor behavior of SrO and TiO₂, or BaO and TiO₂ doped (Na_0.5K_0.5)NbO₃ ceramics is not a Debye type in the radio frequency range.