Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics
AbstractThe potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na)/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions) and different atmospheres (i.e., defect chemistry) on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT). View Full-Text
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Malič, B.; Koruza, J.; Hreščak, J.; Bernard, J.; Wang, K.; Fisher, J.G.; Benčan, A. Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics. Materials 2015, 8, 8117-8146.
Malič B, Koruza J, Hreščak J, Bernard J, Wang K, Fisher JG, Benčan A. Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics. Materials. 2015; 8(12):8117-8146.Chicago/Turabian Style
Malič, Barbara; Koruza, Jurij; Hreščak, Jitka; Bernard, Janez; Wang, Ke; Fisher, John G.; Benčan, Andreja. 2015. "Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics." Materials 8, no. 12: 8117-8146.