Physico-Chemical nanomaterials science

Cd content dependent properties of Ni1-xCdxFe2O4 nano ferrites synthesized without post-preparation thermal treatment
Verma, R.1, Kane S.N.1, Tatarchuk T.2,*, Deshpande, U. P. 3, Mazaleyrat F.4
1 School of Physics, D.A. University, Khandwa Road, Indore 452001, India 
2 Chemistry Department, Vasyl Stefanyk Precarpathian National University, Ivano-Frankivsk, 76018, Ukraine, tatarchuk.tetyana@gmail.com
3 UGC-DAE CSR, Khandwa Road, Indore 452001, India
4 SATIE, ENS University Paris-Saclay, CNRS 8029, F-94230 Cachan, France

Spinel ferrites of general formula Me2+O.Fe3+2O3, display: fcc structure, have two inter-penetrating sub-lattices A (tetrahedral), B (octahedral). Control on structural properties, magnetic properties, bandgap, can be achieved by a specific synthesis protocol, compositional variation, thermal treatment/or no post- preparation thermal treatment etc. Tailorability of structural properties, leads to specific magnetic properties, useful in various applications: bioscience, high frequency devices, microwave devices etc. This work reports, synthesis of 'dry gel' Ni1-xCdxFe2O4 (x = 0.0 − 0.72) nano ferrites, prepared by sol-gel auto-combustion method by utilizing citrate/nitrate precursors. Structural, magnetic studies were done respectively by Cukα x-ray diffraction 'XRD' (to get structural parameters), vibration sample magnetometery (to get Coercivity 'Hc', saturation magnetization 'Ms'). Bandgap is obtained by Ultraviolet–visible (UV–Vis) diffuse reflectance data. Surface morphology, elemental analysis, obtained respectively by ‘SEM’ (Scanning Electron Microscopy), EDS (Energy Dispersive spectroscopy). 
XRD validates the incorporation of Cd2+ ion in fcc spinel nano-ferrite (grain diameter: 13.8  28.6 nm), with linear increase of lattice parameter (0.8344  0.8367 nm), ascribed to higher ionic radius of Cd2+ (0.097 nm) than Ni2+ (0.069 nm). Presence of Fe2O3, phase is ascribable to synthesis at lower temperature and, no post-preparation thermal treatment. Cd2+ ion addition shows: i) increase of Fe3+; decrease of Ni2+ population on B-site, while Cd2+ ions are distributed almost equally on A, B site, showing changes in degree of inversion (0.61  0.90), variation of oxygen parameter between 0.3800 − 0.3892; ii) fine-tuning of bandgap between 1.45  1.6 eV, is of use for fabrication of semiconductor devices, iii) SEM images display agglomerated particles, EDS shows peaks related to all elements in the studied samples, iv) modification of Ms (41.1  46.4 Am2/kg ), Hc (106.6  157.2 Oe) is attributed to re-distribution of cations, strengthening of BB, weakning of AA, AB super-exchange interaction. Antistructure modeling provides information on the types of surface active centers.