Phase transitions and electrical properties of (1−<i>x</i>)(K_0.5Na_0.5)NbO₃−<i>x</i>BiScO₃ lead‐free piezoelectric ceramics with a CuO sintering aid

Abstract

Abstract (1− x )(K 0.5 Na 0.5 )NbO 3 − x BiScO 3 doped with 1 mol% CuO (KNN‐BS‐Cu‐ x ) lead‐free piezoelectric ceramics were prepared by the solid state reaction technique. With the CuO doping, all the ceramics can be well sintered at 1090–1150 °C and exhibit a perovskite structure. After the substitution of BiScO 3 , the polymorphic phase transition (PPT) was shifted to near room temperature; besides, the cubic–tetragonal phase transitions were also shifted to lower temperatures and a relaxor behavior was induced. The ceramic ( x = 0.018) with PPT near room temperature exhibited excellent electrical properties ( d 33 = 224 pC/N, k p = 0.40, and T C = 331 °C). A relatively high mechanical quality factor (288) was also obtained in this particular composition. All these results reveal that KNN‐BS‐Cu‐ x ceramics may become promising candidates for lead‐free piezoelectric materials.