Control of the doping sites of Ho³⁺ in BaTiO₃ by a water-soluble precursor method

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Controlling the substitution sites of Ho³⁺ in BaTiO₃ was demonstrated with a water-soluble precursor method in a relatively high concentration region. Ho³⁺ was added in three different manners to replace either Ba²⁺ or Ti⁴⁺, or both Ba²⁺ and Ti⁴⁺ as Ba_1−xHo_x TiO₃ (A-site substitution), Ba Ti_1−xHo_xO_3−x/2 (B-site substitution) and Ba_1−x/2Ho_x/2 Ti_1−x/2Ho_x/2 O₃ (A/B-sites substitution). The substitution sites were carefully investigated with X-ray diffraction, elemental mapping analysis, X-ray absorption fine structure analysis and the electric properties measurements. The results revealed the difference in the properties such as solubility, local environments around the lanthanides and electric properties depending on the substitution site, which indicated the successful control of the substitution sites simply with the starting composition of the solution. The compositional uniformity of the water-soluble precursor was advantageous in controlling the substitution sites of a rare-earth in BaTiO₃.