High-Energy Storage Properties over a Broad Temperature Range in La-Modified BNT-Based Lead-Free Ceramics

Area of Science:

• Materials Science
• Ceramics
• Energy Storage

Background:

• High-performance energy storage materials are crucial for miniaturized and integrated advanced pulse power capacitors.
• Lead-free ceramics are sought after to replace lead-based materials due to environmental concerns.

Purpose of the Study:

• To design and develop high-performance lead-free energy storage ceramics based on the BNT-BT system.
• To enhance energy storage properties through phase adjustment and domain control via lanthanum doping.

Main Methods:

• Synthesized lead-free [(Bi0.5Na0.5)0.94Ba0.06]1-1.5xLaxTiO3 (BNT-BT-xLa) ceramics.
• Employed a strategy of phase adjustment and domain control through La3+ doping.
• Utilized a two-step sintering approach for microstructural optimization.
• Investigated dielectric relaxation, crystal structure, and energy storage performance (Wrec, η).
• Evaluated frequency stability, thermal endurance, fatigue resistance, and pulse charge-discharge characteristics.
• Performed finite element analysis to simulate the breakdown process.

Main Results:

• La3+ doping improved crystal structure symmetry and induced dielectric relaxation, promoting polar nanoregions.
• At x = 0.12, a recoverable energy density (Wrec) of ~5.93 J/cm3 and efficiency (η) of 77.6% were achieved at 440 kV/cm.
• Two-step sintering further improved performance to Wrec = 6.69 J/cm3 and η = 87.0%.
• Materials exhibited excellent frequency stability (0.5-500 Hz), thermal endurance (25-180 °C), and fatigue resistance (10^5 cycles).
• Ultrashort discharge times (t0.9 ~ 75-89 ns) were observed.
• Fine grains were identified as key to high breakdown strength, hindering crack propagation.

Conclusions:

• Lanthanum-doped BNT-BT ceramics offer a promising lead-free alternative for high-energy storage capacitors.
• The combination of doping and optimized sintering enhances dielectric properties and energy storage performance.
• The materials demonstrate excellent stability and rapid discharge capabilities, suitable for demanding applications.