Softening effect of trace Fe-substituted potassium-sodium niobate-based lead-free piezoceramics

For KNN-based lead-free piezoceramics, Fe usually enters the B site as the acceptor to harden the ceramics. Herein, Fe preferentially entered the A-site, and different softening effects were observed in trace Fe-substitution KNN-base ceramics. The effects of Fe doping on the phase structure, grain size and electrical properties of 0.96K0.48Na0.52Nb0.96Sb0.04O3-0.04Bi0.5-xFexAg0.03Na0.47ZrO3 (KNNS-BFxANZ, x = 0.0~0.08) ceramics were investigated. The most excellent overall properties (kp=0.56, d33=464 pC/N and TC=240 °C) were obtained with x = 0.06. The enhanced electrical properties are attributed to the substantial improvement in density and polarization efficiency caused by trace Fe ions. Of particular interest is that the trace Fe ions doping could regulate the TR-O/TO-T without the change of TC. This work provided a refreshing thinking for the study of soft/hard doping of KNN based piezoelectric ceramics, and was of great significance to further improve the comprehensive properties of KNN based piezoelectric materials without sacrificing Curie temperature. •Softening effect was observed in Fe doped KNN-based piezoelectric ceramics.•The trace Fe ions doping could regulate the TR-O/TO-T without changing the TC.•The most excellent electrical properties (kp=0.56, d33=464 pC/N) were obtained with x=0.06.