Strain‐mediated electrical and optical properties of novel lead‐free CuFe₂O₄–KNbO₃ nanocomposite solid solutions: A combined experimental and Density Functional Theory studies

Abstract

This article summarizes the strain‐mediated electrical and optical properties of novel lead‐free xCuFe2O4 (1 − x) KNbO3 (x = 0.2, 0.3, and 0.4) multiferroic nanocomposite through a solid state route. X‐ray diffraction analysis divulges the influence of interfacial strain in the KNbO3–CuFe2O4 matrix and shows the coexistence of orthorhombic and cubic spinel phases, respectively. Morphological analysis reveals that the average particle size of 0.3CuFe2O4–0.7KNbO3 is 25 nm which is smaller than the other two nanocomposites. The UV–visible absorption studies and Raman spectroscopy of 0.3CuFe2O4–0.7KNbO3 nanocomposite present the high energy bandgap and electro coupling of KNbO3 and CuFe2O4 phases. The DFT theoretical bandgap behaviors of all the three nanocomposites synchronize with the experimental bandgap results. Dielectric, ferroelectric and magnetoelectric behaviors are also improved in 0.3CuFe2O4–0.7KNbO3 nanocomposite as compared to pristine KNbO3 and the other two nanocomposites. Highlights This article summarizes the strain‐mediated electrical and optical properties of novel lead‐free xCuFe2O4–(1 − x) KNbO3 (x = 0.2, 0.3, and 0.4) multiferroic nanocomposite through a solid state route. X‐ray diffraction analysis divulges the influence of interfacial strain in the KNbO3–CuFe2O4 matrix and shows the coexistence of orthorhombic and cubic spinel phases, respectively. The 0.3CuFe2O4–0.7 KNbO3 nanocomposite shows a remarkable increase in the optical bandgap, remnant polarization, dielectric permittivity, and magnetoelectric coefficient compared to the other two nanocomposites. DFT calculations on KNbO3–CuFe2O4 matrix reveal the impact of diffusion between two phases and support the bandgap experimental results.

Oxygen octahedra distortion‐induced multiferroic properties of Er and Zr co‐doped BiFeO3 nanoparticles

“…Further, the origination of tensile strain is due to the contrast of coherence and non‐coherence lattice, along with the variations in the volume of the unit cell. As a result, the XRD peaks are shifted toward a lower angle and experience an effective cohesion between ferroelectric and ferromagnetic phases in this systems 31 …”

“…This is due to the influence of strain between the ferroelectric and ferromagnetic phases 45 . The dominant response of the magnetoelectric coupling coefficient in Bi 0.95 Er 0.05 Fe 0.98 Zr 0.02 O 3 is due to the uniform distribution of grain size and stiffness of ferroelectric and ferromagnetic phases producing significant piezoelectric coefficient and/or magnetostrictive effect 46,47 . As the concentration of Er and Zr increases further in BiFeO 3 , the magnetoelectric coupling decreases.…”

“…As a result, the XRD peaks are shifted toward a lower angle and experience an effective cohesion between ferroelectric and ferromagnetic phases in this systems. 31 Figure 4A-F presents the surface morphological images of Bi 1−x Er x Fe 1−y Zr y O 3 (x = .05, .1; y = 0, .02, .05) polycrystalline nanoparticles. Here, the average grain size is calculated using ImageJ, 32 and the average size distributions of Bi 1−x Er x Fe 1−y Zr y O 3 (x = .05, .1; y = 0, .02, .05) particles are found to be 71.29, 73.74, 78.88, 79, 98.13, and 97.95 nm, respectively.…”

“…45 The dominant response of the magnetoelectric coupling coefficient in Bi 0.95 Er 0.05 Fe 0.98 Zr 0.02 O 3 is due to the uniform distribution of grain size and stiffness of ferroelectric and ferromagnetic phases producing significant piezoelectric coefficient and/or magnetostrictive effect. 46,47 As the concentration of Er and Zr increases further in BiFeO 3 , the magnetoelectric coupling decreases. The reduction of magnetoelectric coupling is due to the demagnetization effect of Zr 4+ ions and the formation of additional phases, which reduces an intrinsic strain between ferroelectric and ferromagnetic phases.…”