Effect of ZnO doping on (K,Na)NbO3-based lead-free piezoceramics: Enhanced ferroelectric and piezoelectric performance

Abstract Potassium sodium niobate (KNN)-based materials are promising lead-free candidates for replacing lead zirconate titanate (PZT)-based piezoelectric materials. Chemical modification of KNN-based compositions has been a fundamental approach for achieving high performance. However, the understanding of donor doping and acceptor doping in KNN-based materials is still under-developed, compared to that in the PZT-based system. In the present study, we investigated the doping effect of ZnO on a KNN-based ceramic with the composition of 0.92(K0.5Na0.5)NbO3-0.02(Bi0.5Li0.5)TiO3-0.06BaZrO3. ZnO was found to exhibit donor doping effect, significantly enhancing the ferroelectricity and piezoelectricity, accompanied by a major contribution to the suppressed formation of oxygen vacancy. Optimized properties (d33 = 350 pC/N, d33* = 507 pm/V, Pr = 18.4 μC/cm2) were obtained in the sample with 0.3 wt% ZnO doping. The discovery of the donor doping of ZnO is important to the development of KNN-based piezoelectric materials as it provides a refreshing perspective on the defect chemistry of the KNN-based materials.