Orientation dependence of electrical properties of large-sized sodium potassium niobate lead-free single crystals

Lead-free (K 0.25 Na 0.75 )NbO 3 (KNN25/75) single crystals with dimensions of Ø30 × 10 mm were successfully grown by a top seeded solution growth technique (TSSG). The X-ray diffraction pattern shows that the as-grown crystals possess an orthorhombic perovskite structure. The concentrations of K, Na, and Nb elements in the as-grown crystal were measured by X-ray fluorescence analysis. The dielectric, ferroelectric and piezoelectric properties of KNN25/75 crystals with different orientations, i.e. , pseudocubic (100) and (110) ((100) pc and (110) pc ), were investigated. A higher piezoelectric constant d 33 ~ 145 pC N −1 and electromechanical coupling coefficient k t ~ 69% were observed along the (100) pc orientation compared with d 33 ~ 70 pC N −1 and k t ~ 51% along (110) pc . However, when a bipolar electric field was applied, a two times higher strain value can be achieved in crystals oriented along (110) pc than along (100) pc . These orientation dependent physical properties can be explained in the framework of domain engineering and the switching effect. Large-sized sodium potassium niobate lead-free single crystals were successfully grown by a top seeded solution growth technique (TSSG).