**2. Experimental procedure**

Synthesis of Cobalt-Erbium nano-ferrites with citrate-gel auto combustion technique was taken up with starting materials Cobalt Nitrate (Co (NO3)26H2O), Ferricnitrate (Fe (NO3)39H2O), Erbium Nitrate (Er (NO3).6H2O), Citric Acid (C6H8O7H2O) and Ammonia solution (NH3) of 99.9% purity after weighing as per stoichiometric ratio. Later liquification of metal nitrates in distilled water was done and the mixture was stirred at 300 rpm for one hour to obtain a clear homogeneous solution. Next citric acid in aqueous form and metal nitrate was maintained in 1:3 ratio for all samples. Now, ammonia solution was added drop by drop to maintain Ph = 7. This solution on stirring was heated at 100°C temperature for ten to twelve hours to form a viscous gel. The water contained in the mixture gets evaporated slowly to form dry gel generating internal combustion to form a black colored

*Crystal Chemistry, Rietveld Analysis, Structural and Electrical Properties of Cobalt… DOI: http://dx.doi.org/10.5772/intechopen.98864*

desired sample. This sample was manually grinded and subjected to calcinations at 500°C in furnace for 4 hours. The step by step procedure for the synthesis of crystal ferrites is shown in the form of flow chart in **Figure 1**. Pellet was prepared with KBr hydraulic press (Model: M-15) in 2–3 mm thickness and 10 mm diameter size

Later these samples in pellet or powder form were used to characterize the material. Structural properties were analyzed with XRD (Bruker, CuKα, λ = 0.15406 nm), TEM (Model JEOL 2100F, Japan), Field-emission Scanning Electron Microscope (JEOL JSM-7600 F, Japan), Energy Dispersive X-ray Analyzer (EDAX) and, Atomic Force Microscopy (AFM: VEECO, USA). Two probe method was used to study electric properties.
