The dielectric and ferroelectric properties of (Ba0.5Sr0.5)TiO₃-doped (Bi0.5Na0.5)TiO₃ lead-free ceramics

Abstract

This work prepares (Ba 0:5 Sr 0:5 )TiO 3 (BST)-doped (Bi 1=2 Na 1=2 )TiO 3 (NBT) lead free ceramics through conventional solid reaction method and analyzes the doping effect of BST on phases, microstructure, dielectric and ferroelectric properties. The phase and structure of the NBT-BST ceramics were investigated through X-ray diffractometer (XRD) and Raman. The XRD results showed that BST has diffused into the NBT lattices to form a stable solid solution; while, Raman spectrum showed the bands at low frequency are different with that of pure NBT and divided into two ranges around 247 cm À1 and 303 cm À1 . Relative dense and homogeneous ceramic microstructures could be achieved, with the observation of a slight decrease in average grain size with the increase of BST doping content. The dielectric and ferroelectric properties were also investigated. The dielectric constant increases gradually with increasing the temperature to T m , and then decrease. The temperature dependence property showed diffused phase transition near T m . The polarization-electric field (P-E) hysteresis loops of BST-doped NBT ceramics showed typical ferroelectric or relaxor nature. Both the E c and P r increased first, then decreased with respect to the increase of the BST content.

Phase coexistence and large piezoelectricity in BaTiO3‐CaSnO3 lead‐free ceramics

“…The permittivity value at T C is largest, which can also be found its implication from Figure . Based on the Landau‐Ginzburg thermodynamic model calculations, for the ferroelectric phase composition, the energy barrier completely disappears near T C , and the vanishing of energy barrier can facilitate a large polarization change in the presence of the electric field resulting in larger permittivity. (ii) this is attributed to the formation of adaptive states under the condition of the near‐vanishing polarization anisotropy near the ferroelectric‐paraelectric phase coexistence region, which is the reason for large intrinsic and extrinsic dielectric property .…”