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Initial stage sintering mechanism of NaNbO3 and implications regarding the densification of alkaline niobates

Koruza, Jurij and Malič, Barbara (2014):
Initial stage sintering mechanism of NaNbO3 and implications regarding the densification of alkaline niobates.
In: Journal of the European Ceramic Society, 34 (8), pp. 1971-1979, ISSN 09552219,
[Online-Edition: http://dx.doi.org/10.1016/j.jeurceramsoc.2014.01.035],
[Article]

Abstract

The behavior of submicron- and nano-sized NaNbO3 powder compacts during conventional sintering was studied using optical dilatometry and microstructure analysis. Microstructure-development trajectories revealed the dominance of grain growth during the initial sintering stage, while densification occurred only during later stages. Surface diffusion with low activation energy in the range of 50–60 kJ/mol was found to be the dominant material-transport mechanism during the initial sintering stage. The early activation of surface diffusion reduced the sintering driving force, decreased the rate of the densifying mechanisms and was thus identified as the main cause for poor densification of NaNbO3. Same explanation could be valid also for other alkaline niobate based lead-free piezoelectric ceramics. Finally, alternative sintering methods are discussed and the efficiency of the pressure-assisted sintering was demonstrated in successful production of highly-dense fine-grained NaNbO3 ceramics, with relative density and grain size of 98% and 700 nm, respectively.

Item Type: Article
Erschienen: 2014
Creators: Koruza, Jurij and Malič, Barbara
Title: Initial stage sintering mechanism of NaNbO3 and implications regarding the densification of alkaline niobates
Language: English
Abstract:

The behavior of submicron- and nano-sized NaNbO3 powder compacts during conventional sintering was studied using optical dilatometry and microstructure analysis. Microstructure-development trajectories revealed the dominance of grain growth during the initial sintering stage, while densification occurred only during later stages. Surface diffusion with low activation energy in the range of 50–60 kJ/mol was found to be the dominant material-transport mechanism during the initial sintering stage. The early activation of surface diffusion reduced the sintering driving force, decreased the rate of the densifying mechanisms and was thus identified as the main cause for poor densification of NaNbO3. Same explanation could be valid also for other alkaline niobate based lead-free piezoelectric ceramics. Finally, alternative sintering methods are discussed and the efficiency of the pressure-assisted sintering was demonstrated in successful production of highly-dense fine-grained NaNbO3 ceramics, with relative density and grain size of 98% and 700 nm, respectively.

Journal or Publication Title: Journal of the European Ceramic Society
Volume: 34
Number: 8
Uncontrolled Keywords: Sintering; Microstructure; Lead-free; Piezoceramics; Alkaline niobates
Divisions: Study Areas
Date Deposited: 09 Dec 2014 13:31
Official URL: http://dx.doi.org/10.1016/j.jeurceramsoc.2014.01.035
Identification Number: doi:10.1016/j.jeurceramsoc.2014.01.035
Funders: This research was financially supported by the Slovenian Research Agency (Young Researcher program, Contract Nos. 1000-08-310121 and P2-0105).
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