Pyrolysis-controlled synthesis and magnetic properties of sol–gel electrospun nickel cobaltite nanostructures

Inducing Superparamagnetism and High Magnetization in Nickel Cobaltite (NixCo3–xO4) Spinel Nanoparticles by Controlling Ni Mole Fraction and Cation Distribution

“…8 λ represents the degree of inversion of the spinel structure, with values 0 and 1 for direct and inverse spinels, respectively. As has been reported by Kumar et al, 16 the ∼645 cm −1 Raman band (A 1g mode) shifts toward a higher wavenumber when the spinel lattice transforms from inverse to partially inverse or normal spinel. 16 Since this A 1g mode is the characteristic vibrational mode of CoO 6 octahedron units, it can be utilized to monitor the effect of Ni incorporation in the Co 3 O 4 crystal lattice.…”

“…On the other hand, magnetic properties of Ni–Co-based oxides have been the subject of intense scientific research due to their potential applications in spintronics, exploiting their intrinsic ferrimagnetic order and metallic electrical behavior . However, understanding the magnetic behavior of NiCo 2 O 4 remained unclear due to contradicting results published in the literature, − especially on its saturation magnetization ( M s ) values. The reported M s values per formula unit of NiCo 2 O 4 vary from ∼6.25 emu/g (0.26 μ B ) to ∼38.0 emu/g (1.58 μ B ).…”

“…The reported M s values per formula unit of NiCo 2 O 4 vary from ∼6.25 emu/g (0.26 μ B ) to ∼38.0 emu/g (1.58 μ B ). In some cases, the room temperature M s value is inexplicably low (∼2 emu/g or 0.086 μ B ). ,− Also, there is no consensus whether all the Ni cations are located at octahedral sites ( O h ) of NiCo 2 O 4 spinel . The reason for such a discrepancy probably lies in the presence of impurities (such as NiO, Ni x Co 1– x O y , α/β-Ni­(OH) 2 , α/β-Co­(OH) 2 , Co 3 O 4 , cobalt carbonates, etc.)…”

“…10,13−15 Also, there is no consensus whether all the Ni cations are located at octahedral sites (O h ) of NiCo 2 O 4 spinel. 16 The reason for such a discrepancy probably lies in the presence of impurities (such as NiO, Ni x Co 1−x O y , α/β-Ni(OH) 2 , α/β-Co(OH) 2 , Co 3 O 4 , cobalt carbonates, etc.) in varied amounts, which also affect the technological application of NiCo 2 O 4 spinel such as in a supercapacitor and lithium ion battery (LIB).…”

Graphene nanoclusters embedded nickel cobaltite nanofibers as multifunctional electrocatalyst for glucose sensing and water-splitting applications

“…which is responsible for sensing behaviour. A closely related phenomena is the transformation of inverse spinel to normal spinel with increase in calcination soaking time [45], Essentially, the Ni cations meet the electrolyte at the surface of the material as they move from tetrahedral to octahedral voids in the crystal structure and facilitates fast electron transfer across the interface [13,29]. However, maintaining an optimal soaking time is also necessary as the particle shape needs to be retained.…”