Sucrose auto-combustion synthesis of Al3+ and Cr3+ substituted LaFeO3 ceramic perovskite: Structural, magnetic, and electrical characterizations

A comparative study for elaborating structural, magnetic, and electrical characteristics of solid solutions LaFe_1-yA_yO₃ (y = 0.0 to 0.5 and A is either Cr⁺³ or Al⁺³) prepared via sucrose sol-gel auto-combustion route. The structure of the samples was studied using X-ray diffraction (XRD), which proved the orthorhombic perovskite structure formation of all samples except for the sample with an Al-content of 0.5. The estimated crystallite sizes, as well as lattice parameters, showed a steady decline as substitution increased, owing to their ionic radii. FT-IR indicated a noticeable shift in the band centers of octahedral sites in the Al-substituted system with successive substitution. TEM exhibited agglomerated sphere-like. The Al-substituted system indicated both antiferromagnetic and ferromagnetic in contrast to the Cr-substituted system, which indicated only anti-ferromagnetic ordering. The obvious increase in the magnetization with successive substitution was discussed in relation to the obtained crystallite sizes. AC-conductivity measurements indicated semi-conducting behavior with increasing conductivity by increasing substitution ratio, especially with chromium-substituted samples. The formed Al₂O₃ secondary phase for the sample with the Al-content of 0.5 indicated an obvious reduction in its estimated electromagnetic properties.