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<p>Lead-free amorphous films are highly competitive candidates for thin-film capacitors due to several advantageous properties, including high breakdown field strength (<i>E</i><sub>b</sub>), excellent stability, and environmental friendliness. However, their relatively low energy storage density has constrained their widespread adoption. To optimize the relation between polarization and breakdown electric field, entropy (<i>S</i>) engineering was employed by doping multiple ions into the amorphous thin films. In this study, we employed conventional Bi<sub>0.5</sub>Na<sub>0.5</sub>TiO<sub>3</sub> (BNT) as the base material and fabricated four compositionally distinct amorphous dielectric films through sol–gel processing, systematically varying the entropy via (i) K/La co-doping at the A-site; (ii) K/La/Sr triple-doping at the A-site; and (iii) Combined K/La/Sr doping at the A-site and Zr doping at the B-site. The equimolar high-entropy Bi<sub>0.2</sub>Na<sub>0.2</sub>K<sub>0.2</sub>La<sub>0.2</sub>Sr<sub>0.2</sub>Ti<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>3</sub> (BNKSLZT) amorphous film (<i>S</i> = 2.30R) demonstrated remarkable performance characteristics, achieving a recoverable energy density of 20.0&#xa0;J&#xa0;cm<sup>−3</sup> at an <i>E</i><sub>b</sub> of 3948&#xa0;kV&#xa0;cm<sup>−1</sup> while retaining an outstanding energy storage efficiency of 83.6%, which is a significant improvement of the energy density by over 2 times and efficiency by 134% compared with those of the BNT sample (<i>S</i> = 0.69R). The material exhibited excellent thermal stability across a substantial temperature range (20–140&#xa0;°C), extensive frequency stability (1–100&#xa0;kHz), and superior cycle Life through more than 5× 10<sup>6</sup> cycles. Our findings demonstrate that high-entropy design can effectively leverage the synergistic advantages of multi-element composite effects by the local polymorphic distortion and strong multiple local distortion to enhance energy storage characteristics. Compared to traditional methods, this approach provides a more flexible and valid way to tune the energy storage performance of amorphous dielectric thin films. The high-entropy amorphous films exhibit substantial promise across diverse application domains, notably including power electronics and systems for renewable energy storage.</p>

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The improved dielectric and energy storage performance of Bi0.5Na0.5TiO3-based amorphous films by high-entropy design

  • 期刊论文

  • 发表日期：

    2025年9月11日

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  • Biao Huang,
  • Jiahao Chen,
  • Shan Chen,
  • Yueqiu Gong

摘要

Lead-free amorphous films are highly competitive candidates for thin-film capacitors due to several advantageous properties, including high breakdown field strength (Eb), excellent stability, and environmental friendliness. However, their relatively low energy storage density has constrained their widespread adoption. To optimize the relation between polarization and breakdown electric field, entropy (S) engineering was employed by doping multiple ions into the amorphous thin films. In this study, we employed conventional Bi0.5Na0.5TiO3 (BNT) as the base material and fabricated four compositionally distinct amorphous dielectric films through sol–gel processing, systematically varying the entropy via (i) K/La co-doping at the A-site; (ii) K/La/Sr triple-doping at the A-site; and (iii) Combined K/La/Sr doping at the A-site and Zr doping at the B-site. The equimolar high-entropy Bi0.2Na0.2K0.2La0.2Sr0.2Ti0.5Zr0.5O3 (BNKSLZT) amorphous film (S = 2.30R) demonstrated remarkable performance characteristics, achieving a recoverable energy density of 20.0 J cm−3 at an Eb of 3948 kV cm−1 while retaining an outstanding energy storage efficiency of 83.6%, which is a significant improvement of the energy density by over 2 times and efficiency by 134% compared with those of the BNT sample (S = 0.69R). The material exhibited excellent thermal stability across a substantial temperature range (20–140 °C), extensive frequency stability (1–100 kHz), and superior cycle Life through more than 5× 106 cycles. Our findings demonstrate that high-entropy design can effectively leverage the synergistic advantages of multi-element composite effects by the local polymorphic distortion and strong multiple local distortion to enhance energy storage characteristics. Compared to traditional methods, this approach provides a more flexible and valid way to tune the energy storage performance of amorphous dielectric thin films. The high-entropy amorphous films exhibit substantial promise across diverse application domains, notably including power electronics and systems for renewable energy storage.