IMF2017

Silver lithium niobates Ag_1-xLi_xNbO₃ (ALN) are promising lead-free piezoelectrics. X-ray and dielectric studies revealed that for x ≤ 0.05 ALN solid solutions behave similarly to AgNbO₃ and undergo the same sequence of phase transitions between ferrielectric M₁, antiferroelectric M₂ and M₃, and paraelectric O₁, O₂, T and C phases. ALN with x≥0.06 exhibit normal ferroelectric state and undergo phase transitions between ferroelectric R, antiferroelectric M, and paraelectric T and C phases. Correlation between lattice dynamics and electric order appearance is a main aim of study. High quality Ag_1-xLi_xNbO₃ (0 ≤ x ≤ 0.1) ceramics were prepared by the conventional solid state reaction route. They were examined by linear and nonlinear dielectric response, Raman scattering and DSC investigations. Analysis of the low frequency Raman spectra showed that for x ≤ 0.05 the relaxational frequency significantly slows down at freezing temperature T_f and at the ferrielectric M₁-M₂ phase transition, while maximum of central peak intensity corresponds to the M₂-M₃ maximum of permittivity. For x ≥ 0.06 a significant softening of two low frequency modes is observed when approaching the ferroelectric-antiferroelectric (R-M) phase transition. These characteristic temperatures were confirmed by nonlinear dielectric response which is sensitive to instabilities in physical system. Raman and dielectric studies showed that Nb-ion dynamics plays a crucial role in appearance of specific properties of silver niobate based materials. The modified phase diagram of Ag_1-xLi_xNbO₃ is proposed.