Realization of densified microstructure and large piezoelectricity in KNN ceramics via the addition of oxide additives

• Published in: Journal of materials science. Materials in electronics Vol. 32; no. 15; pp. 20211 - 20224
• Main Authors: Cheng, Yuan, Xing, Jie, Wang, Ting, Wang, Fei, Li, Ruichen, Sun, Xixi, Xie, Lixu, Tan, Zhi, Zhu, Jianguo
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-08-2021; Springer Nature B.V
• Subjects: Additives; Aluminum oxide; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Cobalt oxides; Coupling coefficients; Curie temperature; Grain size; Lead free; Materials Science; Microcracks; Microstructure; Niobates; Niobium oxides; Optical and Electronic Materials; Optimization; Piezoelectricity; Sodium; Tin dioxide
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-021-06525-x

Lead-free potassium sodium niobate [(K, Na)NbO
3
, KNN]-based ceramics have aroused great interest due to their excellent piezoelectricity and high Curie temperature. However, the deteriorative microstructure of KNN-based ceramics restricts their further developments. In this work, various kinds of oxide additives (Al
2
O
3
, Co
2
O
3
, Nb
2
O
5
, SnO
2
and HfO
2
) are introduced into the KNN-based ceramics to increase the grain size and wipe the microcracks to improve their microstructures. Herein, large piezoelectric coefficient values (
d
33
≈ 450–500 pC/N) and high Curie temperature values (
T
C
≈ 255–263 °C) together with high electromechanical coupling coefficient values (
k
p
≈ 0.50–0.56) are obtained in constructed R-O-T multiphase coexisted KNN-based ceramics. Moreover, the KNN ceramic with the addition of Al
2
O
3
exhibits an optimal unipolar strain value (
S
 = 0.124%) and a high inverse piezoelectric constant (
d
33
*
 = 494 pm/V). We believe that our findings provide a simple, effective, and applicable approach to optimize the electrical performances of KNN-based system materials.