Phase evolution and dielectric tuning in samarium and cobalt Co-doped bismuth ferrite nanoparticles via sol–gel synthesis
摘要
Bismuth ferrite (BFO) has emerged as a promising multifunctional material for electronic applications. This study demonstrates that 10% Sm3⁺ substitution in Bi1-ySmyFe1-xCoxO3 effectively suppresses the Bi25FeO40 impurity phase and induces a structural transition from rhombohedral (R3c) to orthorhombic (Pnma) symmetry. Yet, achieving phase-pure nanoparticles through sol–gel synthesis remains challenging. Co doping reduced the average grain size from ~ 85 nm to ~ 42 nm and significantly enhanced the dielectric constant while minimizing dielectric loss at high frequencies, confirming the material’s suitability for tuned electronic applications. Bond length and bond angle analysis from XRD-CIF reconstruction confirmed lattice distortion induced by doping. Morphological characterization using FESEM and TEM demonstrated spherical, uniformly distributed nanoparticles with reduced particle size upon increasing dopant concentration. High-resolution TEM and SAED patterns further verified the polycrystalline nature and consistency with XRD results. Dielectric studies revealed significant trends in dielectric constant, dielectric loss, real and imaginary parts of electrical modulus, dielectric loss per unit volume, and imaginary part of permittivity. The magnetic measurements demonstrate a significant enhancement in saturation magnetization (Ms), which increased from 0.67 emu/g (pure BFO) to 1.85 emu/g for the Bi0.85Sm0.15Fe0.85Co0.15O3 sample. This improvement is supported by an increase in the Bohr magneton (ηB) from 0.037 to 0.103 μB and a rise in the anisotropy constant (Ka) to 7.8 × 104 erg/cm3. These findings highlight the effectiveness of Sm and Co co-doping in tuning the phase structure and dielectric response of BFO nanoparticles, offering pathways for their integration into advanced electronic and energy storage devices.