Compositional range and electrical properties of the morphotropic phase boundary in the Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 system

• Published in: Journal of the European Ceramic Society Vol. 30; no. 4; pp. 971 - 979
• Main Authors: Otoničar, M., Škapin, S.D., Spreitzer, M., Suvorov, D.
• Format: Journal Article
• Language: English
• Published: 01-03-2010
• ISSN: 0955-2219
• DOI: 10.1016/j.jeurceramsoc.2009.10.006

The Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3 (NBT-KBT) system, with its complex perovskite structure, was investigated as a promising material for piezoelectric applications. The NBT-KBT samples were synthesised using a solid-state reaction method and characterised using XRD and SEM. Room-temperature XRD showed a gradual change in the crystal structure from tetragonal in the KBT to rhombohedral in the NBT, with the presence of an intermediate morphotropic region in the samples with a compositional fraction x between 0.17 and 0.25. The fitted perovskite lattice parameters confirmed an increase in the size of the crystal lattice from NBT towards KBT, which coincided with an increase in the ionic radii. Electrical measurements on the samples showed that the maximum values of the dielectric constant, the remanent polarisation and the piezoelectric coefficient were reached at the morphotropic phase boundary (epsilon = 1140 at 1 MHz; Pr = 40 microC/cm2; d33 = 134 pC/N).