Highly Enhanced Piezoelectricity in Nd-Doped (K, Na)NbO ₃ Perovskite Single Crystals

Rare-earth element engineering has emerged as a pivotal strategy for boosting the piezoelectric performance of lead-free piezoelectrics. Herein, we introduce Nd3+ into highly promising lead-free perovskite (K, Na)NbO3 (KNN) single crystals for the first time. High-quality Nd-doped KNN single crystals are grown by the Czochralski method. The incorporation of Nd elements results in a significant increase in the piezoelectric coefficient d33 to 261 pC/N, a 1.57 times larger value compared to undoped KNN. Mechanistic analysis indicates that the highly enhanced piezoelectricity with the Nd doping strategy is caused by modulating the ferroelectric domain structure and reducing the oxygen vacancy concentration. This work provides a doping strategy via rare-earth-element doping to improve the KNN single crystals.