Co2O3 doped (Na0.65K0.35)NbO3 piezoceramics

Lead-free (Na0.65K0.35)NbO3 + x wt.% Co2O3 (KNN–xCo) piezoceramics were synthesized by conventional ceramic processing and the effects of low Co2O3 concentration on the microstructure and electrical properties were investigated. The experimental results show that the orthorhombic–tetragonal phase transition temperature (TO–T) decreases slightly whereas the tetragonal–cubic phase transition temperature (TC) and crystal structure keep unchanged with the increasing of Co2O3 content. The doping of Co2O3 facilitates the grain growth and improves the density and piezoelectric properties of the ceramics. The sample of x = 0.2 exhibits good piezoelectric properties of piezoelectric coefficient d33 = 127pC/N and electromechanical coupling coefficient kp = 35.1% with density of ρ = 4.31/cm3. These results strongly suggest that the composition of (Na0.65K0.35)NbO3 is another promising lead-free candidate for investigation besides (Na0.5K0.5)NbO3 system.