Influence of lanthanum doping on the dielectric, ferroelectric and relaxor behaviour of barium bismuth titanate ceramics

Abstract

Barium lanthanum bismuth titanate (Ba1−(3/2)xLaxBi4Ti4O15, x = 0–0.4) ceramics were fabricated using the powders synthesized via the solid-state reaction route. X-ray powder diffraction analysis confirmed the above compositions to be monophasic and belonged to the m = 4 member of the Aurivillius family of oxides. The effect of the partial presence of La3+ on Ba2+ sites on the microstructure, dielectric and relaxor behaviour of BaBi4Ti4O15 (BBT) ceramics was investigated. For the compositions pertaining to x ⩽ 0.1, the dielectric constant at both room temperature and in the vicinity of the temperature of the dielectric maximum (Tm) of the parent phase (BBT) increased significantly with an increase in x while Tm remained almost constant. Tm shifted towards lower temperatures accompanied by a decrease in the magnitude of the dielectric maximum (εm) with an increase in the lanthanum content (0.1 < x ⩽ 0.4). The dielectric relaxation was modelled using the Vogel–Fulcher relation and a decrease in the activation energy for frequency dispersion with increasing x was observed. The frequency dispersion of Tm was found to decrease with an increase in lanthanum doping, and for compositions corresponding to x ⩾ 0.3, Tm was frequency independent. Well-developed P(polarization)–E(electric field) hysteresis loops were observed at 150 °C for all the samples and the remanent polarization (2Pr) was improved from 6.3 µC cm−2 for pure BBT to 13.4 µC cm−2 for Ba0.7La0.2Bi4Ti4O15 ceramics. Dc conductivities and associated activation energies were evaluated using impedance spectroscopy.

Investigation of site selectivity of lanthanum in SrBi4Ti4O15 ceramic by structural, dielectric, ferroelectric and conduction behavior

“…layers. Similar kind of observation on the DC conductivity has been reported by Kumar and Verma [40] for La 3? substitution on BBT ceramics.…”

Study of electrical properties of La3+/Mn4+-modified PbTiO3 nanoceramics

“…These vacancies act as the trapping centers for the mobile charge carriers, and the conductivity increases considerably with Mn substitution, via the hopping of charge carriers through available oxygen vacancies. However, these oxygen vacancies are much activated at higher temperature [35,36]. For higher temperature ranges, the mobility increases, and the activation energy values should decrease as observed in Table 3.…”

Relaxor behaviour in BaBi4Ti4O15 ceramics fabricated using the powders obtained by mechanochemically assisted synthesis route

“…In most reports, BBT starting powders were synthesized via the solidstate reaction route by mixing the constituent oxides followed by different calcination steps at high temperatures (950 + 1050 °C) with intermittent grindings (Pribošič et al 2001;Hou et al 2006;Kumar and Varma 2009. However, there exists few reports on the preparation of BBT powders using non-conventional methods such as the Pechini method (Murugan et al 2006), sol-gel (Xie and Pan 2003;Rout et al 2009), templated grain growth (Kimura and Yoshida 2006), and molten-salt synthesis (Huang et al 2011).…”