Hu Liang,Xia Yuting,Wang Qianqian,Yang Hui,Zhang Qi-long
In this work, a core–shell dendritic CuO@TiO 2 was constructed through a two-step chemical method. Structural analysis confirms the successful coating of TiO 2 on the CuO and the dendritic morphology was maintained after the coating process. The composites were prepared by using ferroelectric P(VDF-HFP) as matrix and synthesized particles as filler. The introduction of fillers influences the melting and crystallization process of the polymer matrix without altering the composition. The insulator layer suppresses the conductivity and dielectric loss by blocking the charge carriers while the composites exhibit improved dielectric constant in the frequency wide range of 10 2 –10 6 Hz and enhanced thermal conductivity. The composite with 20% CuO@TiO 2 exhibits a high dielectric constant of 51.7, low loss of 0.11 at 1 kHz and high thermal conductivity of 0.382 W/mK, showing huge potential for dielectric applications.
Weiqian Song,Yangxi Yan,Maolin Zhang,Dongyan Zhang,Li Jin,Zhimin Li
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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