Systematic investigation of the influence of magnetic and non-magnetic ion substitutions in BiFeO3 under similar internal chemical pressure

Polycrystalline Bi_1-xR_xFeO₃ (RHo and Y, x = 0.00, 0.05 and 0.10) compounds were prepared to perform a systematic investigation of the role of chemical nature and effect of internal chemical pressure on the structural, microstructural, magnetic, electric, ferroelectric and optical properties of the compounds. Structural analysis revealed that lattice distortions observed in Ho and Y-substituted compounds were not the same. The lattice parameters were larger in the case of the Y-substitution compared to the Ho-substituted counterpart. Scanning electron micrographs confirmed the formation of dense, well-connected grains exhibiting a reduction in size with increasing substitution. The magnetic properties of BiFeO₃ were enhanced through the suppression of the spin structure with the substitution. The substitution of magnetic (Ho³⁺) ions led to an improvement in remanent magnetization and coercive field, whereas the substitution of non-magnetic (Y³⁺) ions resulted in enhanced maximum magnetization with negligible coercive field at room temperature. The ferroelectric measurements evidenced that both remanent polarization and coercive fields improved in substituted compounds, attributed to a decrease in charge carriers. Furthermore, the Y³⁺ ion substitution positively influenced ferroelectric properties by reducing leakage currents compared to the Ho³⁺ ion substitution. The optical absorption measurements indicated a decrease in the energy band gap of BiFeO₃ with substitution, implying alterations in the material's optical characteristics. The ac conductivity studies demonstrated a discernible reduction in the conductivity of the substituted compounds. Specifically, Ho-substitution exhibited a more pronounced magnitude in the decline in conductivity relative to Y-substitution. This outcome signifies the potential efficacy of Ho-substitution in exerting control over the insulating characteristics of the compounds.