Phase evolution and associated electrical properties of Al-doped KNN-Bi0.5Na0.5ZrO3 lead-free piezoelectric ceramics

Samples of Al-doped (1-x)K0.5Na0.5Nb0.965Sb0.035O3-x(Bi0.82Al0.18)(0.5)Na0.5ZrO3[((1-x)KNNS-xBANZ)] (x = 0.02, 0.03, 0.04, and 0.05) have been prepared by a conventional solid-state method. The results of XRD analysis suggest that the ceramics underwent a typical phase transition from orthorhombic (0) to tetragonal (T) as x was increased. According to the Raman shifts of key vibrational modes, lattice deformation and associated phase transition have been qualitatively deduced. Moreover, the ceramic with x = 0.05 exhibits enhanced piezoelectric properties compared with K0.5Na0.5NbO3 due to an O-T phase boundary (d(33 )approximate to 258 pC/N and k(p) approximate to 0.40). More importantly, the mechanism through which small ions function in a KNN lattice, as well as the phase transition, is addressed herein.