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<p>(K, Na)NbO<sub>3</sub> (KNN) is regarded as a promising lead-free piezoelectric candidates due to its high Curie temperature and environmental compatibility. However, its piezoelectric performance remains inferior to Pb-based ceramics, mainly due to the rigid lattice and high coercive field that restrict domain switching. In this study, CaHfO<sub>3</sub> was introduced to modify the perovskite structure of KNN through a homologous co-doping mechanism. The simultaneous substitution of Ca<sup>2+</sup> and Hf<sup>4+</sup> modifies the local bonding environment and induces lattice softening, which effectively reduces the coercive field and facilitates polarization switching. At the optimal composition of 0.95(K<sub>0.5</sub>Na<sub>0.5</sub>)NbO<sub>3</sub>-0.02(Bi<sub>0.5</sub>Na<sub>0.5</sub>)ZrO<sub>3</sub>-0.03CaHfO<sub>3</sub> (0.95KNN-0.02BNZ-0.03CHO), the ceramics exhibit significant improvements in both ferroelectric and piezoelectric properties, while maintaining a balanced Curie temperature. This work provides clear evidence that structural softening induced by Ca-Hf incorporation provides an effective materials design strategy for enhancing the performance of lead-free KNN-based ceramics, while the compositional limits and long-term device-level behavior require further investigation.</p>

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Enhanced piezoelectric performance and thermal stability in KNN-BNZ ceramics modified by CaHfO3

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月13日

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  • Kai Zheng,
  • Ning Xie,
  • Li-Feng Zhu,
  • Jiao Jin,
  • Pengfei Liu

摘要

(K, Na)NbO3 (KNN) is regarded as a promising lead-free piezoelectric candidates due to its high Curie temperature and environmental compatibility. However, its piezoelectric performance remains inferior to Pb-based ceramics, mainly due to the rigid lattice and high coercive field that restrict domain switching. In this study, CaHfO3 was introduced to modify the perovskite structure of KNN through a homologous co-doping mechanism. The simultaneous substitution of Ca2+ and Hf4+ modifies the local bonding environment and induces lattice softening, which effectively reduces the coercive field and facilitates polarization switching. At the optimal composition of 0.95(K0.5Na0.5)NbO3-0.02(Bi0.5Na0.5)ZrO3-0.03CaHfO3 (0.95KNN-0.02BNZ-0.03CHO), the ceramics exhibit significant improvements in both ferroelectric and piezoelectric properties, while maintaining a balanced Curie temperature. This work provides clear evidence that structural softening induced by Ca-Hf incorporation provides an effective materials design strategy for enhancing the performance of lead-free KNN-based ceramics, while the compositional limits and long-term device-level behavior require further investigation.