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Home  >  Journal list  >  Journal of the Ceramic Society of Japan ( 2003 - 2007 )  >  Vol.114  No.1329 (May) (2006)  >  pp.386-391

Journal of the Ceramic Society of Japan ( 2003 - 2007 )
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Grain Size and Piezoelectric Properties of (Ba, K, Na)NbO3 Lead-Free Ceramics

Shinjiro TASHIRO1) and Keisuke ISHII1)
1) Department of Materials Science and Engineering, The National Defense Academy

  Grain size and piezoelectric properties were investigated in (K, Na)NbO3 ceramics substituted with Ba for K and Na by 1 to 5 mol%, in anticipation of high piezoelectric properties. The grain size strongly depended on the A/B ratio in perovskite structure. The grain growth phenomenon was markedly similar to that of BaTiO3 semiconducting ceramics with donor additives. Piezoelectric properties were strongly affected by grain size. MnO additive was added to suppress grain growth anomaly, dense ceramic body formation and withstanding voltage enhancement. However, a manufacturing process, in which MnCO3 was directly mixed to other raw material powders, resulted in the formation of large pores ranging to 1 mm diameter in their ceramic bodies. The powder obtained by previously calcining the mixture of Nb2O5 and MnCO3 was used as a raw material for MnO addition, in order to prevent the formation of large pores. By adding 0.5 mol% MnO, grain growth anomaly was inhibited, and a uniform and dense ceramic body was consequently obtained without piezoelectric property degradation.

Lead-free, Piezoelectric ceramic, Sr substitution, A/B ratio, KNbO3, NaNbO3, MnO addition, Grain growth anomaly, Donor dopant

Received: January 18, 2006
Accepted: March 16, 2006 , Published online: May 01, 2006
Copyright (c) 2006 The Ceramic Society of Japan



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