Structural and impedance spectroscopic studies of CuO-doped (K0.5Na0.5Nb0.995Mn0.005O3) lead-free piezoelectric ceramics
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- Kamal, A., Rafiq, M.A., Rafiq, M.N. et al. Appl. Phys. A (2016) 122: 1037. doi:10.1007/s00339-016-0564-z
Polycrystalline lead-free (1 − x)(K0.5Na0.5)(Nb0.995Mn0.005O3)–xCuO ceramics where 0 ≤ x ≤ 2% were synthesized using the conventional solid-state reaction method. X-ray diffraction analysis confirmed the presence of single-phase possessing monoclinic symmetry for all the synthesized compositions. Scanning electron microscopy revealed a dense microstructure along with increase in grains size with Cu doping in the KNNMn ceramics. Impedance spectroscopy (IS) showed that Cu doping was found to be helpful in increasing the grain boundary resistance. A temperature-dependent and non-Debye-type relaxation process was also revealed by IS studies. The relaxation time for both bulk and grain boundary decreased with temperature indicating a hopping conduction mechanism. The activation energy was found to be 0.4–0.5 eV, indicating conduction of oxygen vacancies through hopping mechanism. Insights gained from this work could be useful in designing the optimum composition and microstructure of KNN-based ceramics for practical applications.