Cobalt ions doped PNN-PHT ceramics with excellent piezoelectric properties
In this study, Co-doped 0.49 Pb(Ni 1/3 Nb 2/3 )O 3 -0.51 Pb(Hf 0.3 Ti 0.7 )O 3 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 Co 2+ in the lattice. The introduction of Co 2+ effectively increased grain size, improved ferroelectric properties , reduced leakage current density, and enhanced electromechanical coupling coefficient k p . 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 d 33 ~780 pC/N, electromechanical coupling coefficient k p ~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.
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