BNT-based relaxor/ferroelectric systems: Improved field-induced strain property in the layered composite ceramics

Both high strain and low driving electric-field are important characteristics of the piezoelectric actuators for industrial applications, but they are difficult to achieve together in a single material system. In this work, the layered and inlay-onlay structures of relaxor/ferroelectric composites were prepared by selecting relaxor phase (0.94Bi(0.5)(Na0.82K0.18)(0.5)TiO3-0.06NaNbO(3), BNKT-6NN) and ferroelectric phase (0.9Bi(0.5)Na(0.5)TiO(3)-0.1Bi(0.2)Sr(0.7)TiO(3), BNT-10BST) with the volume ratio of 1:1. By comparing the field-induced strains under same electric-field, the S-33 of the BNKT-6NN/BNT-10BST layered composites (0.17%) was greater than that of the inlay-onlay composites (0.08%) and exhibited excellent temperature stability. The superiority in field-induced strain for the layered composite ceramic was originated from the inhomogeneous distribution of internal electric-field between relaxor and ferroelectric phase and thereby could modulate the polar nanoregions to ferroelectric phase transition. In addition, the restricted phase boundary between relaxor and ferroelectric phase enhanced the potential barrier energy (E-a = 1.47 eV) and hindered the jump of defective ions (mainly oxygen vacancies) of the BNKT-6NN/BNT-10BST layered composites. The outstanding electrical properties of layered composite ceramics provide a new idea for further improving field-induced strain performance.