Orientation Dependence of Dielectric and Relaxor Behaviour in Aurivillius Phase BaBi₂Nb₂O₉ Ceramics Prepared by Spark Plasma Sintering

Grain-oriented Aurivillius phase BaBi ₂ Nb ₂ O ₉ ceramics were fabricated using Spark Plasma Sintering (SPS). Their relaxor behaviour was confirmed by a strong frequency dispersion of the dielectric response. The dielectric behaviour has been fitted using different relaxor models. The relaxor parameters are isotropic, while the dielectric constants are highly anisotropic. The piezoelectric constant d ₃₃ is zero perpendicular and parallel to the hot pressing direction, and the P–E response is dominated by losses. The inability to pole the samples at room temperature is consistent with the τ _ƒ temperature ( ~ ~115 K) estimated from fitting the experimental data to the Vogel–Fulcher model. This suggests that it may be possible to observe piezoelectric and ferroelectric properties at very low temperatures.