Synthesis and structural evolution of BaLaTiBiO solid solutions (0.0 ≤ x ≤ 0.05).

In this study, the synthesis and structural evolution of pure BaTiO and BaTiO co-doped with La and Bi, produced using the ball milling method and heat treatment, were analyzed. The starting materials included chemically pure precursor powders of BaCO, TiO, LaO and BiO. Stoichiometric calculations were performed using the BaLaTiBiO mechanism with concentrations x = 0.0, 0.0025, 0.0045, 0.006, 0.01, and 0.05 (mol %). The structural and morphological evolution of the samples was characterized by x-ray diffraction (XRD), Rietveld refinement, and high-resolution scanning electron microscopy (HRSEM-EDS). XRD and Rietveld refinement results indicated a tetragonal ferroelectric phase for samples with x ≤ 0.006. As doping levels increased, a peak disappearance was observed, corresponding to a phase transformation from tetragonal to cubic at x = 0.01. Additionally, a cubic secondary phase, BaBiO₃, was detected at x = 0.05, indicating that the maximum solubility of La³⁺ and Bi³⁺ ions in BaTiO was exceeded at this concentration. The concentration x = 0.0025 was found to exhibit the maximum tetragonality among the samples studied, with a value of 1.0087, greater than the tetragonality for pure BaTiO, 1.0083. The HRSEM-EDS analysis revealed that for samples with x ≤ 0.006, the microstructure consisted of faceted shape grains with mean grain size in the range of 362.5 nm-488.3 nm. Punctual microanalysis and elemental distribution mapping of the doped samples showed that the grains were composed of Ba, Ti, O, Bi, and La, which were homogeneously distributed, confirming the incorporation of the dopant elements into the BaTiO structure.