Origin of anomalous giant dielectric performance in novel perovskite: Bi0.5−xLaxNa0.5−xLixTi1−yMyO3 (M = Mg2+, Ga3+)

Abstract

Dielectric properties and dielectric relaxation behaviors of A/B sites co-substituted Bi0.5Na0.5TiO3 perovskite-type ferroelectrics are reported. The Bi0.5−xLaxNa0.5−xLixTi1−yMyO3 (M = Mg2+, Ga3+) exhibits anomalous giant dielectric permittivity (ε’) of ~105 under a heterogeneous constitution with easily discernible grain and grain boundary conductivity. The lone pairs substitution theory as well as extrinsic disorders are used to clarify the significant structural evolution and the origin of the dielectric performance. A bigger free volume promotes the anomalous relaxation between oxygen sites, and the polarization direction on the nanoscale deviates from the average polarization direction at its ferroelectric state. Furthermore, no obvious phase transition indicates the considerable static substitutional disorder at the Bi/Na sites, which facilitates delocalized conduction of oxygen ions in the intermediate temperature range.

Colossal permittivity behavior and its origin in rutile (Mg1/3Ta2/3)xTi1-xO2

“…Furthermore, it is noteworthy that the colossal permittivity materials design based on the EPDDs have been extended to other host materials systems, such as perovskite materials 10, 17, 18, 48 . It is timely important to draw people attention on the complexity and difference of defect design in solids.…”

“…As the CP is determined by the defect rather than the average structure, the preparation approach and process conditions of the synthesis of CP materials are therefore critical, affecting the formation of defect structures and thus influencing the dielectric behavior. This makes reported dielectric properties of In + Nb co-doped rutile TiO 2 very diverse 18–23 . Intrinsically, an excellent CP property with a low dielectric loss can be achieved mainly or at least dominantly from EPDD 20, 21 or from the localized electrons associated with the coexistence of Ti 3+ and Nb 4+ presented in the samples 22, 23 .…”

High energy storage density over a broad temperature range in sodium bismuth titanate-based lead-free ceramics

“…The reason is that BNT belongs to perovskite-type ferroelectric with an A-sites disorder structure and Bi 3+ ion is a promising alternative to Pb 2+ ion due to their similar lone-pair electronic 6   s 2 configuration 1, 25 . Generally, the dielectric property of BNT shows three dielectric anomalies with increasing the temperature 26 . They are the shoulder with a strong frequency dependent of dielectric constant anomaly at ~200 °C, the peak with a broad dielectric constant maximum at ~325 °C, and the hump of dielectric loss (depolarization temperature, T d ) at a low temperature of ~190 °C 26–29 .…”

“…Generally, the dielectric property of BNT shows three dielectric anomalies with increasing the temperature 26 . They are the shoulder with a strong frequency dependent of dielectric constant anomaly at ~200 °C, the peak with a broad dielectric constant maximum at ~325 °C, and the hump of dielectric loss (depolarization temperature, T d ) at a low temperature of ~190 °C 26–29 . The double dielectric constant peaks for BNT-based ceramics can be modified by the introduction of other components 26–28, 30 .…”

“…where W 1 is the energy storage density, ε 0 is the dielectric constant of free space (8.854 × 10 −12  F/m), ε ′ is the dielectric constant of materials and E is applied electric field (kV/cm). In addition, the occupation of Li + and La 3+ ions in A-sites tend to shrink the lattice owing to the formation of oxygen vacancies and smaller ionic sizes of Li + and La 3+ than those of Na + and Bi 3+ (ionic radii: 1.39, 1.38, 1.36, and 0.92 Å for Na + , Bi 3+ , La 3+ , and Li + ) 26, 31, 32 . It is well known that Ti 4+ and Zr 4+ possess the identical valence, but Zr 4+ has more chemical stablity and larger ionic size.…”