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Rare earth (RE) elements (Tb, Tm) doped K0.5Na0.5NbO3 (KNN) lead-free ceramics were fabricated using conventional solid-state reaction method. All samples with dominating orthorhombic phase are well developed. The effects of Tb and Tm on impedance, dielectric and ferroelectric properties are systematically studied. There are relaxation-like features of the ceramics after the doping of RE elements. Conduction processes were affected by defect, especially in KNN-Tb ceramics, in the higher temperature region. The doping of Tb and Tm increases density, remnant polarization and the piezoelectric constant of the KNN ceramics due to the effect of donor doping. The overall analysis has confirmed the significance of RE elements (Tb, Tm) doping in KNN and shows that it is a promising candidate as lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Rare earth (RE) elements (Pr, Sm) doped K0.5Na0.5NbO3 (KNN) lead-free ceramics were fabricated using conventional solid-state reaction method and their properties were investigated. The X-ray methods indicate that Pr and Sm ions diffuse into the KNN lattice to form new homogenous solid solutions. After the doping of RE elements, the grain size decreases obviously and the phase structure translates from orthorhombic to pseudo cubic phase. The RE ions enter into the A-site of the KNN lattice to create new A-site vacancies, exhibiting "soft" characteristics. Existence of two semicircular arcs represents both grain and grain boundary property of the materials. The results of Ea indicate that oxygen vacancies dominate the conductivity properties of the ceramics from 425 to 525 °C The photoluminescence spectra of KNN + Pr exhibits orange emissions. Both the KNN + Sm and KNN + Pr/Sm ceramics exhibit yellowish green emission upon 406 nm light excitation. RE elements Pr and Sm-doped KNN ceramics may take an important role in many fields as multifunctional materials. [ABSTRACT FROM AUTHOR]