Study On The Effect Of Multi-doping On The Construction Of KNN Ceramic Phase Boundary And Piezoelectric Properties

KNN-based piezoelectric ceramics are considered to be one of the materials most likely to replace lead zirconate titanate（PZT）because of their high Curie temperature and better mechanical quality factors.By doping different ABO₃perovskite structure oxides in KNN,different phase boundaries were constructed in KNN,and the mechanism of phase boundary construction and piezoelectric performance enhancement mechanism were studied.The（1-x）K_0.5Na_0.5Nb O₅-xBi(Zn_0.5Zr_0.5)O₃was prepared by solid-phase sintering.The results showed when x=0.008,the orthogonal-tetragonal（O-T）coexisting phase structure was constructed at room temperature.The sample with x=0.008 had the highest piezoelectric constant d₃₃=238 p C/N,and in the range of 25℃～300℃,d₃₃remained stable,proving that the system had good temperature stability.The（1-x）(K_0.5Na_0.5)(Nb_0.96Sb_0.04)-x(Ba_0.6Ca_0.4)ZrO₃was prepared by solid-phase sintering.The results showed that when x=0.3,R-T coexisting phase structure was constructed at room temperature and d₃₃=238 p C/N.The enhancement of piezoelectric performance was not only related to the intrinsic contribution phase structure,but also the reversal of extrinsic contribution domains.The reversal of electrical domains and the movement of domain walls greatly improved piezoelectric activity.At the same time,the system also had a higher T_c=325℃and good temperature stability.The（1-x）(K_0.5Na_0.5)(Nb_0.96Sb_0.04)-x(Ba_0.5Ca_0.5)HfO₃system was prepared by solid-phase sintering.The results showed that when x=0.03,R-O-T coexisting phase structure was constructed at room temperature.The electro-strain study was conducted on the system,and when x=0.03,the maximum strain is about 14%,which proves that the system has a high piezoelectric response.In addition,the system also had good dielectric,piezoelectric temperature stability and stable frequency dependence,which was beneficial to promote the practical application of KNN-based lead-free piezoelectric ceramics.Figure 33;Table 6;Reference 115...