Flexoelectric aging in barium titanate-based ferroelectric ceramics

Bi(Mg2/3Nb1/3)O3-modified Bi0.5Na0.5TiO3-NaNbO3 lead-free relaxor ferroelectric ceramics with high capacitive energy-storage

Abstract BaTiO 3 –Bi Me O 3 relaxor ferroelectric ceramics are promising for dielectric energy storage applications due to their high dielectric constants, large energy densities, high efficiencies, and excellent thermal stability. However, previous studies have predominantly examined macroscopic performance, leaving the microscopic mechanisms of performance enhancement unclear. This study comprehensively investigated the dielectric energy storage properties of BaTiO 3 and BaTiO 3 –Bi(Zn 1/2 Zr 1/2 )O 3 (BaTiO 3 –BZZ) through integrated experimental and theoretical approaches to decipher the underlying microscopic physical mechanisms. The results demonstrate that the BaTiO 3 –BZZ exhibits significantly enhanced electrical performance relative to pure BaTiO 3 , specifically manifested in superior dielectric breakdown strength (BDS), increased recoverable energy density, and higher energy storage efficiency. First-principles calculations indicate that Zn/Zr substitution at the B -site raises the energy barrier for oxygen vacancies migration in BaTiO 3 , accounting for the observed enhancements in BDS and energy density. Moreover, Zn incorporation reduces the energy barrier for polarization reversal, contributing to improved energy storage efficiency. Polarization switching proceeds via a continuous domain nucleation and growth mechanism rather than a simultaneous bulk reversal. These combined experimental and theoretical findings advance the fundamental understanding of structure-property relationships in BaTiO 3 -based relaxor ferroelectrics and provide insights for designing next-generation high-performance dielectric energy storage materials.

Abstract Ferroelectric ceramics are widely used as actuators, sensors, and energy harvesters. Their coupled electromechanical properties arise from intrinsic polarisation at the lattice scale, with a significant proportion of their bulk properties originating from the mobility of ferroelectric and ferroelastic domains. Separating the intrinsic from the extrinsic contributions to the dielectric properties using Rayleigh analysis is an important characterisation tool for optimising ferroelectric ceramics. This technique is typically conducted on monolithic ceramics with a relative density ( ρ rel ) greater than 0.95, where the effects of porosity on the measured permittivity are neglected, and the local electric field during the measurement of ferroelectric and dielectric properties is assumed to be homogeneously distributed. This study proposes an adjustment to the Rayleigh analysis for porous ferroelectric composites formed using directional freeze-casting, where these assumptions for monolithic ceramics no longer hold. Our experimental results show that the apparent intrinsic contribution scales linearly with the fraction of aligned porosity (1— ρ rel ) due to the reduction of the active ferroelectric volume, despite no significant structural transformations being observed. To address this, a relative density adjustment was introduced, which decouples the intrinsic contribution from ρ rel . The adjusted extrinsic contribution increases with decreasing ρ rel , which is attributed to the reduction in intragranular stress due to the introduction of porosity. The proposed adjustment provides a more accurate characterisation of the intrinsic and extrinsic contributions in freeze-cast porous ferroelectric ceramics, enabling the optimisation of ferroelectric devices with enhanced and reliable properties.

Polymer dielectrics exhibit remarkable advantages, including high power density, elevated operating voltage, and excellent processability. In dielectric films, the ferroelectric domain architecture and its flipping dynamics are pivotal for energy storage, as they govern electric displacement and charge-discharge efficiency. A widely adopted strategy to enhance polarization involves incorporating ferroelectric ceramics into the polymer matrix. However, this approach inevitably induces higher dielectric loss and compromises charge-discharge efficiency. Here a ferroelectric-paraelectric KNbO3-SrTiO3 nanofillers is introduced that effectively suppress ferroelectric domain volume, mitigate hysteresis, and reduces remnant polarization. Phase-field simulations corroborate that domain polarization undergoes more facile reversal, substantially minimizing dielectric loss while preserving high polarization. To further enhance the breakdown strength (Eb), the KNbO3-SrTiO3 filler is encapsulated with an Al2O3 coating. Consequently, the KNbO3-0.2 SrTiO3@Al2O3/FPI nanocomposite film achieves outstanding dielectric capacitor performance, featuring an impressive energy storage density of 6.09 J cm-3, a higher displacement difference (Dmax-Dr) of 2.08 µC cm-3, and an Eb of 611 MV m-1 at 150°C under 100Hz. This work presents a forward-thinking strategy for the scalable industrial production and deployment of high-performance dielectric capacitors.

The investigation of environmentally friendly, Pb-free ceramic dielectric materials with excellent energy storage capability represents a fundamental yet challenging research direction for the development of next-generation high-power capacitors. In this study, linear dielectric Ca0.7La0.2(Mg1/3Nb2/3)O3 was added into [0.65BaTiO3–0.35(Na0.5Bi0.5)TiO3] to form a solid solution. The introduction of Ca0.7La0.2(Mg1/3Nb2/3)O3 modified the crystal structure, enhanced insulation performance and breakdown strength, and reduced hysteresis loss. These improvements collectively contributed to higher energy storage density and efficiency (η). The ceramic pellet with the optimal 10 mol% Ca0.7La0.2(Mg1/3Nb2/3)O3 demonstrated a higher retrievable energy density (~3.40 J cm−3) and efficiency (~81%) at a breakdown strength of 340 kV cm−1 compared to BaTiO3-based ferroelectric ceramics. The sample also exhibited good stability across a temperature range of 30–90 °C and a frequency range of 0.5–300 Hz. Thus, the as-prepared ceramics sample exhibited significant potential for pulsed power device applications.

Transparent ferroelectrics with high linear electro-optic (EO) coefficients are critical for advanced electro-optical devices. However, achieving optical transparency in ferroelectric ceramics remains challenging due to visible light scattering caused by defects such as domain walls, grain boundaries, and pores. Here, we report the successful fabrication of transparent ferroelectric ceramics through innovative chemical composition design and an advanced two-step sintering process in the La-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 system. The optical transparency, which is near the theoretical upper limit, can be attributed to the wide band gap and the minimization of light scattering of defects. By minimizing porosity and engineering grain/domain sizes to differ significantly from the wavelengths of visible light, we suppress scattering, achieving optical transparency near the theoretical upper limit. Strikingly, these ceramics exhibit an ultrahigh linear EO coefficient of ∼1417 pm/V, over 65 times greater than that of LiNbO3 single crystals, the current industry standard. We attribute this exceptional performance to dynamic atomistic polar structures within switchable, thermally stable domains, which enhance electronic polarization sensitivity. This mechanism is corroborated by dielectric spectroscopy, high-resolution transmission electron microscopy and simulation. Our findings offer insights into the design of cost-effective transparent materials with exceptional EO properties, paving the way for next-generation electro-optical devices.

Enhancement in energy storage density perfomances via the generation of ploymorphic nano polar phases in ferroelectric ceramics

Dielectric breakdown in ferroelectric ceramics: The influence of coating uniformity

Prominent cryogenic fluorescence temperature sensing and superior room-temperature photochromism in Bi/Eu codoped KNN transparent-ferroelectric ceramics

Superior energy storage and stability in antiferroelectric-doped relaxor ferroelectric ceramics

Improved energy storage behavior and thermal stability of (1-x)KTa0.63Nb0.37O3-xBi(Mg0.5Ti0.5)O3 ferroelectric ceramics

Multi-mode optical modulation and superior energy storage in Eu/La co-doped KNN transparent ferroelectric ceramics

Structural engineering for excellent energy storage and photoluminescence properties in (Bi0.5Na0.5)TiO3 -based lead-free ferroelectrics ceramics

Phase engineering in (Bi0.5Na0.5)0.7Sr0.3TiO3-based relaxor ferroelectric ceramics for improved energy storage performance

Optimized capacitive energy storage in ternary BiFeO3-BaTiO3–NaNbO3 multilayer ferroelectric ceramics

In situ visualisation of the sintering process and phase evolution in Bi2O3-doped Ba0.95Ca0.05Ti0.92Zr0.08O3 lead-free ferroelectric ceramics

Antiferroelectric phase regulation for constructing BNT-based relaxor ferroelectric ceramics: A breakthrough in ultra-high energy storage performance under moderate electric fields

Structures and properties of the Sb-doped PLZT ferroelectric ceramics around the morphotropic phase boundary

Dissipation in two types of ferroelectric lead zirconate titanate ceramics under bipolar electric loading at different frequencies and amplitudes is experimentally investigated. Immersing the specimens in an oil bath and measuring temperatures at some distance allows conclusions to be drawn about the dissipation power, based on a correlation from calibration tests with a Joule heat source. While several mechanisms of self-heating are known to prevail in polycrystalline ferroelectric ceramics, the transition of loading from below to above the macroscopic coercive electric field is of particular interest, revealing the increasing predominance of domain switching, partly leading to mechanical failure. The dissipation power densities presented for different electric load amplitudes and frequencies may eventually provide a valuable opportunity to validate constitutive models of polycrystalline ferroelectrics.