Dielectric, piezoelectric, and electromechanical phenomena in (K0.5Na0.5)NbO3–LiNbO3–BiFeO3–SrTiO3 ceramics

The effect of the substitutions of BiFeO3 (BF) and SrTiO3 (ST) to (Na0.5K0.5)NbO3–LiNbO3 (KNN-LN) ceramics was studied as a candidate of lead-free piezoceramics. The piezoelectric property is enhanced near the phase transition composition caused by the distortion of crystal lattice by Li+ and also the strong ferroelectric nature of BF. The ST was found to be effective in improving the temperature dependence of the KNN ceramics. Small amount of ST also promoted the incorporation of LN and BF into the crystal lattice, and enhanced the piezoelectric performance furthermore. The 94.5(Na0.5K0.5)NbO3-4.5LiNbO3-0.5SrTiO3-0.5BiFeO3 ceramics showed excellent piezoelectric properties of d15=231 pC/N, d33=155 pC/N, and d31=70 pC/N.