Cobalt ions doped PNN-PHT ceramics with excellent piezoelectric properties

Abstract In this study, Co-doped 0.49 Pb(Ni1/3Nb2/3)O3-0.51 Pb(Hf0.3Ti0.7)O3 ceramics with high piezoelectric constants, electromechanical coupling coefficients, and low dielectric losses were prepared by conventional solid-phase reaction method for use as piezoelectric energy harvesters in both resonant and non-resonant working states. XRD results showed the dissolution of Co ions in the crystal lattice, thereby replacing B-sites and transforming the crystal phase into tetragonal phase. Valence states of Co obtained from fitted XPS data confirmed the existence of Co as Co2+ in the lattice. The introduction of Co2+ effectively increased grain size, improved ferroelectric properties, reduced leakage current density, and enhanced electromechanical coupling coefficient kp. Impacts of Co-doping on properties of the as-obtained ceramics were discussed. The optimal performances were obtained at x = 1.25, with piezoelectric constant d33~780 pC/N, electromechanical coupling coefficient kp~0.62, and dielectric loss tan δ = 0.78%. In sum, the excellent piezoelectric properties of Co-doped PNN-PHT ceramics look promising for use as piezoelectric energy harvesters.