Effects of A/B-site dopants on microstructure and domain configuration of potassium sodium niobate lead-free piezoelectric ceramics

In the work, Al, La, Ce and Sn were introduced to investigate effects of A/B-site dopants on microstructure and domain configuration of KNN-based piezoceramics. The results of XRD analysis showed that O phase and T phase coexisted in all the samples and A-site dopants gave rise to expansion of O phase and shrinkage of T phase while B-site dopants played an opposite role in lattice deformation. Moreover, the samples with B-site dopants possessed big c/a which was closely related to Tc. Some step-like grains and the grains with fish-bone stripes were generated in all the samples because the dopants with different melting point influenced grain growth behavior significantly through changing some special crystal faces' growth velocity. Besides, it was verified that high melting point facilitated formation of nanodomains and a novel domain configuration was reasonably deduced according to special spatial orientation of lattice planes observed by HR-TEM in O-T phase coexistence region. In conclusion, comparable piezoelectric properties (d33∼200 pC/N etc.) to K0.5Na0.5NbO3-Bi0.5Na0.5ZrO3 were attained in Al doping ceramics, implying appropriate substitution of Al for Bi was beneficial to lower the cost.