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Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

Malič, Barbara and Koruza, Jurij and Hreščak, Jitka and Bernarding, J. and Wang, Ke and Fisher G., John and Benčan, Andreja (2015):
Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics.
In: Materials, MDPI Publishing, ISSN 1996-1944,
[Online-Edition: http://www.mdpi.com/1996-1944/8/12/5449],
[Article]

Abstract

The 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).

Item Type: Article
Erschienen: 2015
Creators: Malič, Barbara and Koruza, Jurij and Hreščak, Jitka and Bernarding, J. and Wang, Ke and Fisher G., John and Benčan, Andreja
Title: Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics
Language: English
Abstract:

The 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).

Journal or Publication Title: Materials
Publisher: MDPI Publishing
Uncontrolled Keywords: lead-free piezoelectric; KNN; sodium potassium niobate; sintering; microstructure
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Nonmetallic-Inorganic Materials
Date Deposited: 02 Dec 2015 09:01
Official URL: http://www.mdpi.com/1996-1944/8/12/5449
Identification Number: doi:10.3390/ma8125449
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