Cole-cole analysis of a new lead free NaNbO3-Sr0.5NbO3-LiNbO3 ferroelectric relaxor

Dielectric response of (NaNbO3)0.65-(Sr0.5NbO3)0.325-(LiNbO3)0.025 lead-free relaxor ceramic has been studied as a function of frequency over a wide range of temperatures. The relaxor behaviour was evident from the diffused and frequency-dependent dielectric permittivity maximum together with Vogel-Fulcher-like frequency shift of permittivity maximum temperature (T m ). Analysis of the Cole-Cole plots as function of the temperature allowed us to elucidate two different dielectric relaxations and the appearance of a dc conductivity contribution above 100°C. The LF relaxation and dc conductivity have the same activation energy. The HF relaxation is characterised by a distributed relaxation time spectrum described by the well-known Cole and Cole expression. On cooling from 170°C a critical exponent α exhibits a pronounced increase from almost 0 (a Debye-like relaxation) to 0.8 in the vicinity of the Vogel-Fulcher temperature and saturates at lower temperatures. Such behaviour of α corresponds to the broadeni...