High-Efficiency Lead-Free BNT-Based Relaxor Ferroelectrics via Synergistic A/B-Site Substitution for Enhanced Energy...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Dielectric Materials

Background:

• Lead-free dielectrics are crucial for pulsed-power capacitors, but pristine Bi_0.5Na_0.5TiO₃ (BNT) exhibits limitations like high remanence and coercivity.
• Enhancing dielectric properties requires strategies to overcome BNT's inherent drawbacks for efficient energy storage applications.

Purpose of the Study:

• To develop high-efficiency, lead-free dielectric ceramics with improved energy storage capabilities.
• To investigate the effects of multi-cation substitution on the relaxor ferroelectric behavior and dielectric properties of BNT-based ceramics.

Main Methods:

• Synthesis of (1 - x)Bi_0.5Na_0.5Ti_0.97Nb_0.03O₃-xSr_0.85Ba_0.15Ta_0.5+0.02xAl_0.5-0.02xO₃ (BNTNb-SBTA) ceramics via solid-state reaction.
• Characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and dielectric measurements.
• Evaluation of energy storage performance, breakdown strength, and operational stability under various conditions.

Main Results:

• A pure perovskite solid solution was achieved, with grain refinement observed via SEM, suppressing oxygen vacancies and increasing breakdown strength.
• Enhanced relaxor ferroelectric behavior, loop slimming, and a systematic rise in breakdown strength were evidenced by Raman and dielectric analyses.
• The composition with x = 0.10 demonstrated optimal performance, yielding a recoverable energy density (W_rec) of 3.357 J cm^-3 and an efficiency (η) of 90.5% at a breakdown strength (E_b) of 240 kV cm^-1.

Conclusions:

• Synergistic A/B-site disorder and microstructural densification effectively minimize remanent polarization (P_r) while elevating breakdown strength (E_b).
• The developed BNTNb-SBTA ceramics exhibit robust operational stability and fast discharge capabilities, making them suitable for high-efficiency energy storage.
• These lead-free dielectrics offer a promising alternative for pulsed-power capacitor applications requiring high energy density and reliability.