Influence of synthetic route on physico-chemical properties of cadmium ferrites
Munish Gupta, DAV College, Amritsar, Amritsar, IndiaAnu ., BUC College, Batala, Batala (Gurdaspur), IndiaB.S. Randhawa, Guru Nanak Dev University, Amritsar, India
Fundamental electro-magnetic parameters of bulk cadmium ferrites reveal transition from antiferromagnetism to ferrimagnetism during their transformation to nano regime using sol-gel method as a synthetic route. Nanofabrication of ferrites under observation may results from nature of dopant and preparatory conditions applied. These factors may alter cation distributions in ferrite spinel structure and leads to increase in physico-chemical properties of nano-cadmium ferrites because of the large surface/volume ratio than the bulk counterparts. Based on the cation distribution amongst the tetrahedral (A) and octahedral (B) sites of the co-ordinated oxygen, spinel ferrites may be either normal spinel with divalent cation in tetrahedral A-sites and trivalent cation in octahedral B-sites (M2+)A[(Fe3+)2]BO4 or inverse spinel with half of the trivalent ions in the A-sites and the other half together with divalent ions in the B-sites. Many spinels, in particular nanocadmium ferrites, exhibit either partially inverted structure or even a random cation distribution because of the large surface/volume ratios. Inversion parameter, λ, has been used to mark cation distributions in nano-ferrite as (M2+1−λM3+λ)A(M2+λM2+2−λ)BO4. Bulk CdFe2O4, is a normal ferrite with antiferromagnetic nature (λ≈ 0.05). Whereas, its nanocrystalline form possess partial inverse structure with randomly located divalent and trivalent cations in a cubic close-packed structure. Several conventional synthetic approaches like ball milling, ceramic, co-precipitation techniques etc. have been used to synthesize Cd ferrites. In the present talk, synthesis of pure and doped nano-ferrites using sol-gel method has been reviewed. The preparation route followed has advantage over other methods as ferrites in the nano-range are obtained in a single step. Whereas, in conventional ceramic methods, there is formation of bulk ferrites due to sintering over prolonged period.