Phase transitions and dielectric behavior in lead-free ceramics (1-x-y)Na 0.5 Bi 0.5 TiO ₃ -Na 0.5 K 0.5 NbO ₃ -yBiFeO ₃

Ceramic materials (1-x-y)BNT - xNKN - yBFO were synthesized using a traditional solid-state reaction method. Ceramics were examined by X-ray diffraction, microstructural analysis and dielectric methods. The change in symmetry of the crystal lattice in (1-x-y)BNT - xNKN - yBFO has a complex nature, displays the presence of planar defects and compositional heterogeneity. In this system, two phase transitions occur: a morphotropic phase transition from the cubic to the rhombohedral phase occurs by the nucleation and growth type through the morphotropic region in the range of 0.3 < y < 0.5. The second phase transition occurs by spinodal decomposition of the rhombohedral phase into two phases with close cell parameters in the range of 0.6 < y < 0.7. A correlation relationship between the crystal structure, microstructure and dielectric properties in solid solutions of the system was shown.