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<p>The development of lead-free dielectric ceramics that can maintain reliable performance at elevated temperatures remains a significant challenge. In this work, Bi<sub>0.5</sub>(Na<sub>0.78</sub>K<sub>0.22</sub>)<sub>0.5</sub>TiO<sub>3</sub> (BNKT) and a series of Zr- and LaFeO<sub>3</sub>-modified BNKT compositions were synthesized by a conventional solid-state route. Structural analyses, including X-ray diffraction, reveal that LaFeO<sub>3</sub> addition drives a transformation from the coexistence of tetragonal (P4bm) and rhombohedral (R3c) phases to a stable tetragonal (P4bm) perovskite structure, while Zr substitution further modifies local lattice distortions. Raman, ferroelectric, piezoelectric, and dielectric characterizations demonstrate that these co-modifications enhance relaxor characteristics and local structural heterogeneity. This structural evolution significantly enhances the relaxor behavior and improves the temperature coefficient of capacitance. The optimized BNKZT-LF3 sample exhibited a dielectric constant of approximately 4900, maintaining excellent stability within the 155–500&#xa0;°C range (TCC ≤  ± 15%). Notably at 200&#xa0;°C, the dielectric constant remained above 4400, demonstrating significant thermal robustness. These findings underscore the potential of co-modified BNKT ceramics for advanced capacitors and electromechanical applications requiring reliable performance under harsh thermal conditions.</p>

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High-temperature-stable dielectric properties of Zr, LF co-doped BNKT lead-free ceramics

  • 期刊论文

  • 发表日期：

    2026年7月25日

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  • Luu Thi Nhan,
  • Duong Vu Truong,
  • Ngo Thi Hoa,
  • Van-Quyet Nguyen,
  • Minh-Tan Man,
  • Duong Van Thiet

摘要

The development of lead-free dielectric ceramics that can maintain reliable performance at elevated temperatures remains a significant challenge. In this work, Bi0.5(Na0.78K0.22)0.5TiO3 (BNKT) and a series of Zr- and LaFeO3-modified BNKT compositions were synthesized by a conventional solid-state route. Structural analyses, including X-ray diffraction, reveal that LaFeO3 addition drives a transformation from the coexistence of tetragonal (P4bm) and rhombohedral (R3c) phases to a stable tetragonal (P4bm) perovskite structure, while Zr substitution further modifies local lattice distortions. Raman, ferroelectric, piezoelectric, and dielectric characterizations demonstrate that these co-modifications enhance relaxor characteristics and local structural heterogeneity. This structural evolution significantly enhances the relaxor behavior and improves the temperature coefficient of capacitance. The optimized BNKZT-LF3 sample exhibited a dielectric constant of approximately 4900, maintaining excellent stability within the 155–500 °C range (TCC ≤  ± 15%). Notably at 200 °C, the dielectric constant remained above 4400, demonstrating significant thermal robustness. These findings underscore the potential of co-modified BNKT ceramics for advanced capacitors and electromechanical applications requiring reliable performance under harsh thermal conditions.