Densification of tungsten-bronze KBa2Nb5O15 lead-free piezoceramics

✍ Scribed by Ken-ichi Kakimoto; Tomoko Yoshifuji; Hitoshi Ohsato

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 554 KB
• Volume: 27
• Category: Article
• ISSN: 0955-2219
• DOI: 10.1016/j.jeurceramsoc.2007.02.112

✦ Synopsis

Densification of tetragonal tungsten-bronze (TTB) structured KBa 2 Nb 5 O 15 ceramics was studied as a function of extra K 2 CO 3 amounts (δ) ranging from 0 to 5 mol%. The lattice constant c-axis, which corresponds to the spontaneous polarization direction for TTB structure, was remarkably increased compared to a-axis, when δ was increased up to 3. In this case, both of the sintered density and tetragonality of KBa 2 Nb 5 O 15 ceramics were also enhanced, but were deteriorated in the specimens with higher δ than 3, because of the secondary phase precipitation and inhomogeneous microstructure. The enhanced tetragonality observed in the δ = 3 sample resulted in the increase of the Curie temperature (T c ) i.e., the δ = 3 sample demonstrated the highest T c (376 • C) which corresponds to about 96% of T c for the single crystal. Furthermore, diffuse phase transition at T c was suppressed for the δ = 3 sample, because the optimized amount of excess K 2 CO 3 could compensate effectively for the K-loss defect formed in the TTB structure during sintering process.