LAUSR

The figures of merit in the on-resonance and off-resonance conditions (FOMon and FOMoff) for the piezoelectric energy harvester (PEH) were measured and compared in [(K0.485Na0.515)1-XLiX](Nb0.99Ta0.01)O3 (x = 0.04 ~ 0.09) (KNLNT) ceramics with various Li contents. The crystal structure of CuO-doped KNLNT ceramics changes from orthorhombic to tetragonal around the Li fraction of 0.065. The stable temperature range for the tetragonal phase widens to both higher and lower temperatures as Li is substituted. The piezoelectric charge constant (d33), electromechanical coupling factor (kp) and mechanical quality factor (Qm) have maximum values at the Li fraction between 0.055 and 0.065 where the phase boundary lies between the orthorhombic and tetragonal phases. Both FOMon and FOMoff have peak values around the phase boundary but the peak compositions are not exactly coincided. The optimal Li fraction in the KNLNT ceramic for a PEH application was found to be between 0.055 and 0.065.