Sintering and Dielectric Property of (K_{1 − x}Na_x)Ba₂Nb₅O₁₅ Ceramics

Abstract

The crystal structure and dielectric property of tetragonal tungsten-bronze (TTB) structured (K _0.5 Na _0.5 )Ba ₂ Nb ₅ O ₁₅ (KNBN50) ceramics was investigated as a function of extra Na ₂ CO ₃ content (α) ranging from 0 to 3.0 mol%. All the synthesized ceramics showed relative densities higher than 94% of theoretical, and the samples with α ranging from 1.5 to 2.5 demonstrated an enhanced √10 c/a ratio in TTB structure and high T _c around 450°C which is approximately 70°C higher than that of Na-free KBa ₂ Nb ₅ O ₁₅ (KBN) piezoceramics. It is also confirmed that extra Na ₂ CO ₃ could reduce ionic conduction and provide a nomal Curie-Weiss behavior with enhanced dielectric constant maximum.

Keywords:

• Alkali barium niobate
• tetragonal tungsten-bronze structure
• sodium excess
• lattice parameter
• Curie temperature

Acknowledgments

This work was financially supported by a Grant-in-Aid for Scientific Research (C) (No. 19560675) from Japan Society for the Promotion of Science (JSPS), and by Industrial Technology Research Grant Program in 2007 from New Energy and Industrial Technology Development Organization (INEDO) of Japan.