Enhanced dielectric stability and coercivity of band gap tuned Ba–Al Co-doped bismuth ferrite: An experimental and DFT+U investigation

Abstract

Employing a modified sol-gel combustion technique, BiFeO3 and Bi0.85Ba0.15Fe1-xAlxO3 (x = 0, 0.025 and 0.050) nanoparticles were synthesized, and the effects of these dopants were investigated analyzing the experimental findings and adopting the DFT + U approach. Rietveld analysis of XRD revealed a deformed perovskite rhombohedral structure for all the Ba–Al co-doped nanoparticles, which was also validated by theoretical study. Suppression of the low-frequency dispersion promoting outstanding dielectric stability was observed due to Al3+ doping, and the least dielectric constant along with the highest resistivity was reported for BBFAO-2.5. The band gap of co-doped nanoparticles (x = 2.5 & 5) decreased to 1.95 eV and 1.98 eV, respectively, compared to 2.06 eV, and 2.09 eV for BBFAO-0 and pure BFO. The average particle size of all the co-doped nanoparticles was below the repeat length of the cycloid structure, which is favorable for improved magnetic properties. Remanent magnetization, coercivity, and squareness increased as the motion of domain walls is inhibited by the smaller-sized nanoparticles. DFT + U study further endorses the findings of the experimental study. Analysis of DOS revealed the emergence of shallow impurity states around VBM due to doping, which can operate as active trap centers and impede carrier recombination. Thus, it can be inferred that, Ba–Al co-doped nanoceramics with intriguing dielectric, optical, and magnetic properties are a promising candidate for high-frequency microwave devices, magnetic memory and storage devices, near UV-detector, and solar photocatalysis applications.