Balancing Sensitivity and Stability: Comparative Study of La-Doped and Gradient-Doped KNN Piezoelectrics*

Lead-free piezoelectrics based on potassium sodium niobate (K₀.₅Na₀.₅NbO₃, KNN) are promising alternatives to lead-based ceramics for sustainable energy and sensing applications. A central challenge is to achieve both large piezoelectric response and long-term thermal stability. In this work, we compare two complementary doping strategies: lanthanide (La³⁺) substitution and layered/gradient doping.

Recent studies demonstrate that layered dopant distributions in KNN can simultaneously enhance piezoelectricity and stabilize performance across wide temperature ranges by generating internal fields and engineered domain configurations [1]. Other work shows that lanthanide doping induces large strain responses and improves domain wall mobility near polymorphic phase transitions [2].

Building on these insights, we synthesized and characterized both La-doped and gradient-doped KNN ceramics. Dielectric and displacement measurements reveal that La doping produces sharp enhancements in piezoelectric response, while gradient doping provides improved stability and fatigue resistance over broad operating conditions. This comparative study identifies tradeoffs between sensitivity and stability in KNN-based lead-free piezoelectrics and suggests design principles for environmentally friendly sensors and actuators.

References

1. A. Song, Y. Liu, T. Feng, H. Li, Y. Zhang, X. Wang, L. Liu, B.-P. Zhang, and J.-F. Li,
   
   “Simultaneous enhancement of piezoelectricity and temperature stability in KNN-based lead-free ceramics via layered distribution of dopants,”
   
   Adv. Funct. Mater. 32, 2204385 (2022). https://doi.org/10.1002/adfm.202204385
   
   A. Song, Y. Liu, T. Feng, H. Li, Y. Zhang, X. Wang, L. Liu, B.-P. Zhang, and J.-F. Li,
   
   “Large strain response in lanthanide-doped potassium sodium niobate-based piezoceramics,”
   
   Ceram. Int. 49, 1627–1636 (2023). https://doi.org/10.1016/j.ceramint.2022.10.039