Composition driven ferroelectric transformations in lead-free Ba(Ti1−xCex)O3 (0.02 ≤ x ≤ 0.10)

• Dielectric and x-ray structural studies on heterophase Ba(Ti1−xCex)O3 are performed.
• Phase contents are interpreted in terms of domains and stress-relief conditions.
• Role of domain types in complete stress relief at relatively small x is described.
• Key role of single-domain Amm2-phase interlayers in heterophases is first emphasized.
• Agreement between predicted and experimental phase contents at 0.02 ≤ x ≤ 0.10 is stated.

The Ce-modified lead-free Ba(Ti1−xCex)O3 system is studied with regard to its dielectric and structural phase-transformation behaviour as a function of composition. Detailed Rietveld analysis of x-ray powder diffraction patterns revealed that the system exhibits orthorhombic (Amm2) + tetragonal (P4mm) phase coexistence for x = 0.02, pure orthorhombic (Amm2) for 0.02 < x < 0.07 and orthorhombic (Amm2) + rhombohedral (R3m) phases for 0.07 ≤ x ≤ 0.10. Heterophase states of the Ba(Ti1−xCex)O3 system are analyzed taking into account domain (twin) types and stress-relief conditions at interphase boundaries. This analysis enables us to consider the role of specific domain types in a complete stress relief even at relatively small values of x. Volume fractions of the ferroelectric phases coexisting in samples are found using the volume fractions of some domain types in these phases at 0.02 ≤ x ≤ 0.10. Results of our calculations and experimental studies on the volume fractions of the coexisting phases are consistent.