A comprehensive study of the phase diagram of K0.5Na0.5NbO3-Bi0.5Na0.5TiO3 system

The phase diagram of lead-free piezoelectric (1-x)K0.5Na0.5NbO3-xBi0.5Na0.5TiO3 system has been studied by high-resolution synchrotron powder diffraction, neutron powder diffraction and selected area electron diffraction (SAED). The two lead-free piezoelectric compounds, K0.5Na0.5NbO3 and Bi0.5Na0.5TiO3 tend to form an infinite solid solution. The oxygen octahedral tilt system has been mapped as a function of composition and temperature. The results indicate that K0.5Na0.5NbO3-Bi0.5Na0.5TiO3 does not display a morphotropic phase boundary like lead zirconate titanate, and that the most significant structural change as a function of composition occurs near x=0.14 and x=0.87 due to ionic disorder at A and B sites in the perovskite ABO3 structure at room temperature.