Ultrahigh Energy‐Storage Density in NaNbO₃‐Based Lead‐Free Relaxor Antiferroelectric Ceramics with Nanoscale Domains

Abstract

Dielectric energy-storage capacitors have received increasing attention in recent years due to the advantages of high voltage, high power density, and fast charge/discharge rates. Here, a new environment-friendly 0.76NaNbO 3 -0.24(Bi 0.5 Na 0.5 )TiO 3 relaxor antiferroelectric (AFE) bulk ceramic is studied, where local orthorhombic Pnma symmetry (R phase) and nanodomains are observed based on high-resolution transmission electron microscopy, selected area electron diffraction, and in/ex situ synchrotron X-ray diffraction. The orthorhombic AFE R phase and relaxor characteristics synergistically contribute to the record-high energy-storage density W rec of ≈12.2 J cm −3 and acceptable energy efficiency η ≈ 69% at 68 kV mm −1 , showing great advantages over currently reported bulk dielectric ceramics. In comparison with normal AFEs, the existence of large random fields in the relaxor AFE matrix and intrinsically high breakdown strength of NaNbO 3 -based compositions are thought to be responsible for the observed energy-storage performances. Together with the good thermal stability of W rec (>7.4 J cm −3 ) and η (>73%) values at 45 kV mm −1 up to temperature of 200 °C, it is demonstrated that NaNbO 3 -based relaxor AFE ceramics will be potential lead-free dielectric materials for next-generation pulsed power capacitor applications.

Superior Energy‐Storage Capacitors with Simultaneously Giant Energy Density and Efficiency Using Nanodomain Engineered BiFeO3‐BaTiO3‐NaNbO3 Lead‐Free Bulk Ferroelectrics

“…W rec values in relaxor FEs and purely linear nonpolar dielectrics are usually restricted by limited P max values under high fields owing to low E B value and low ε r value, respectively. AFE ceramics usually exhibit relatively good energy‐storage properties owing to high P max , particularly for relaxor AFEs showing even better energy‐storage performances . However, it is particularly worthy of note in current work that superior comprehensive properties through excellent balance between W rec (≈8.12 J cm −3 ) and η (>90%) values have been realized in BF‐based relaxor FEs with x = 0.1 owing to inherently high P s , high applied field, and fast polarization response, showing huge advantages for the application in pulsed power electronics.…”

“…A large W rec of 3.98–4.81 J cm −3 as well as a large η of >85% can be obtained in the temperature range of –50 to 250 °C in the studied composition. A detailed comparison was made in Figure S4, Supporting Information with some other recently reported dielectric ceramics, demonstrating obvious advantages in the thermal stability of the x = 0.1 sample. Moreover, no evident change in I max and I – t curves can be seen in the temperature range from room temperature to 200 °C, as shown in Figure S3, Supporting Information and Figure f, resulting in a temperature‐insensitive W D of ≈2.5 J cm −3 under 20 kV mm −1 in Figure f.…”

“…Therefore, the composition system with intrinsically high spontaneous polarization ( P s ) should be crucial for achieving excellent energy‐storage performances. Among various types of dielectrics, antiferroelectric (AFE) materials have exhibited obvious advantages so far, thus achieving a continuous rise of recently reported W rec values . However, the hysteresis of the electric field induced phase transition in AFEs during charging and discharging is inherently responsible for inadequate energy efficiency (η), even for most relaxor AFEs in which high energy density has to compromise seriously with the efficiency and even the thermal stability.…”

“…However, it is particularly worthy of note in current work that superior comprehensive properties through excellent balance between W rec (≈8.12 J cm −3 ) and η (>90%) values have been realized in BF‐based relaxor FEs with x = 0.1 owing to inherently high P s , high applied field, and fast polarization response, showing huge advantages for the application in pulsed power electronics. Compared with relaxor AFEs, which show obvious advantages in the aspect of W rec (≈7.02 and ≈12.2 J cm −3 in BNT‐ and NN‐based relaxor AFEs, respectively), BF‐based relaxor FEs prove to show obviously large advantages in energy‐storage efficiency (≈85% and ≈69% in BNT‐ and NN‐based relaxor AFEs, respectively), as long as limited E B can be effectively improved.…”

Multifunctional barium titanate ceramics via chemical modification tuning phase structure

“…B1‐B3, Evolution of ε r ‐ T curves, P ‐ E loops, and W rec , W loss and η for BT‐based ceramics with the ferroelectric phase, relaxor phase, and crossover state between them. C, Distribution of W rec and η for BT‐, BNT‐, BFO‐, KNN‐, NN‐, ST‐, AN‐, and Pb‐based ceramics 129,165‐206 . D1, ε r ‐ T curves of BaTiO 3 ‐ x K 0.73 Bi 0.09 NbO 3 (BT‐ x KBN) ceramics at 1 kHz.…”