Raman spectroscopy, dielectric properties and phase transitions of Ag0.96Li0.04NbO3 ceramics

Silver lithium niobates Ag1−xLixNbO3 are promising lead free piezoelectrics. Good quality Ag0.96Li0.04NbO3 ceramics were obtained. Dielectric and DSC studies showed that, in comparison to AgNbO3, temperatures of phase transitions slightly decrease. Dielectric studies pointed to enhancement of polar properties. Remnant polarisations achieves value of 0.6 μC/cm2. Maximum of ϵ(T) dependences related to the relaxor-like ferroelectric/ferrielectric M1–M2 transition becomes higher and more frequency dependent. Analysis of Raman spectra showed that two modes at 50 and 194 cm−1 exhibit significant softening. Low frequency part of the Raman spectra which involve central peak and soft mode were analysed using two models. CP was assumed as relaxational vibration and described by Debye function. The slope of temperature dependences of relaxational frequency γR(T) changes at approximately 470 and 330 K, indicating that slowing down process of relaxational vibrations changes in the vicinity of partial freezing of Nb-ion dynamics Tf and further freezing at ferroelectric/ferrielectric phase transition.