Complex structural contribution of the morphotropic phase boundary in Na0. 5Bi0. 5TiO3-CaTiO3 system

Roy Roukos, Sara Abou Dargham, Jimmy Romanos, Denis Chaumont

Research output: Contribution to journalArticleAcademicpeer-review


The correlation between structure and dielectric properties of lead-free (1-x)Na0.5Bi0.5TiO3 - xCaTiO3 ((1-x)NBT - xCT) polycrystalline ceramics was investigated systematically by X-ray diffraction, combined with impedance spectroscopy for dielectric characterizations. The system shows high miscibility in the entire composition range. A morphotropic phase boundary (MPB), at 0.09 ≤ x < 0.15 was identified where rhombohedral and orthorhombic symmetries coexist at room temperature. The fraction of orthorhombic phase increases gradually with x in the MPB region. Dielectric measurements reveal that the relative permittivity increase with addition of Ca2+. This behavior is unusual with this kind of doping. A thermal hysteresis occurred only in the MPB composition which varies in a non-monotonically manner with x, detected by dielectric properties. This phenomenon is related to the crystalline microstructure by a linear relationship between the fraction of each phase and dielectric properties, and, more precisely, to the strong interaction between rhombohedral and orthorhombic phases.
Original languageEnglish
Pages (from-to)4467-4473
Number of pages7
JournalCeramics International
Issue number4
Publication statusPublished - Mar 2019
Externally publishedYes


  • morphotropic phase boundary (MPB)
  • x-ray diffraction
  • dielectric properties
  • thermal hysteresis
  • NBT-CT


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