High‐permittivity and conduction mechanism of La‐doped Ba_0.67Sr_0.33TiO₃ ceramics

Abstract

High permittivity La‐doped Ba0.67Sr0.33TiO3 ceramics (BSTL) with cubic perovskite structure, i.e., BaxSr1−xTiO3 (BST) + x at.% La, where x = 0–1, were prepared by conventional ceramic processing techniques. Dielectric characteristics, X‐ray diffraction, scanning electron microscopy (SEM), and J–V (leakage current density–voltage) behaviors were measured. Doping with the La in the BST host lattice resulted in a large‐grained (1–3 µm) and fine‐grained (0.3–1 µm) microstructure, marked raising, and broadening of the Curie peak. The temperature of dielectric peak (Tm) at 10 kHz decreased rapidly with a doping concentration of <0.7 at.% La. By means of doping with La, high dielectric constant ceramics (BSTL: 0.2 ≤ x ≤ 0.7) with permittivity at room temperature (εRT) > 110 000 at 10 kHz have been achieved. The plots of leakage current density versus voltage show the different electrical conduction mechanism in different voltage ranges.

The effect of titanium excess and deficiency on the microstructure and dielectric properties of lanthanum doped Ba0.55Sr0.45TiO3 with colossal permittivity

“…BSTs in the paraelectric state show low losses (<0.01) over a wide temperature range making them feasible for high frequency applications. [8,9] In the BST material family colossal permittivity has previously been observed in lanthanum doped Ba0.67Sr0.33TiO3 [4]. The study showed a promising room temperature colossal relative permittivity over 130,000 and a tan  of 0.068 at 10 kHz with 0.7 at.% addition of lanthanum.…”

“…Behaviour of the loss curve is similar to that of the permittivity, being high at low frequencies while decreasing to less than 0.05 between 30-40 kHz. High permittivity values at low frequencies can be due to the built-up of charge at the grain-grain boundary or electrodesample interface which causes a large polarization [4]. The +Ti025 sample showed a similar behaviour to that of the Ti0 sample.…”

“…Furthermore, at higher temperatures and frequencies the losses rapidly increased. [4] In the case of other lanthanum doped BST compositions: Ba0.60Sr0.30TiO3 [10], Ba0.74Sr0.26TiO3 [11] and Ba0.8Sr0.2TiO3 [12], no colossal permittivity has been observed. Ba0.60Sr0.30TiO3 showed a room temperature permittivity of 2750.2 and tan  of 0.0137 at 10 kHz with 0.5 mol.% of lanthanum addition i.e.…”

“…In recent years colossal permittivity (>10 4 ) materials have gained research interest in the field of electro-ceramics. Materials with high permittivity and low dielectric losses are attractive for numerous electrical applications and enable further miniaturization of dielectric components and have the potential for increased energy density in capacitors.…”

“…Materials with high permittivity and low dielectric losses are attractive for numerous electrical applications and enable further miniaturization of dielectric components and have the potential for increased energy density in capacitors. Colossal permittivities have been reported for several doped material systems such as TiO2 [1], BaTiO3 [2], CaCu3Ti4O12(CCTO) [3] and Barium Strontium Titanates (BSTs) [4]. Using various novel sintering methods or atmospheric conditions, colossal permittivity has also been observed in systems without specifically added dopants in the case of BaTiO3 [5], SrTiO3 [6] and BST [7].…”