Effect of Li2O-doping of CdO/Fe2O3 system on the formation of nanocrystalline CdFe2O4

The solid–solid interactions between pure and Li2O-doped cadmium and ferric oxides have been investigated using DTA and XRD techniques. A mixture of equimolar proportions of powdered cadmium nitrate and ferric oxide were impregnated with lithium nitrate dissolved in the minimum amount of water making a paste. The paste was calcined at 500–1000 °C. The amounts of dopants were 0.75, 1.5 and 3 mol% Li2O.The results obtained showed that the addition of lithium nitrate to the reacting mixed solids enhanced the thermal decomposition of cadmium nitrate. Pure Fe2O3 interacted readily with CdO at temperatures starting from 600 °C yielding crystalline CdFe2O4 phase. This phase was produced at 500 °C upon doping the mixed oxides with 1.5 or 3 mol% Li2O. The degree of reaction propagation increased as a function of temperature up to 800 °C. The crystallite size of the produced CdFe2O4 was reduced due to Li2O-doping to the nanocrystalline range upon doping with 3 mol% Li2O. Raising the calcination temperature to 1000 °C effected the decomposition of a portion of the formed CdFe2O4 and exerted an opposite effect on the crystallite size. Doping of the investigated system followed by calcination at 500–800 °C enhanced the CdFe2O4 formation to an extent proportional to the amount of Li2O added. The decomposition of CdFe2O4 was accompanied by an endothermic peak at 965 °C and Li2O-doping enhanced the decomposition process. The activation energy of formation of CdFe2O4 (ΔE) was determined for pure and doped solids and the computed values were 67, 58, 42 and 25 kJ mol−1 for pure solids and those doped with 0.75, 1.5 and 3 mol% Li2O, respectively. The decrease in the ΔE values was attributed to the role of Li2O in increasing the mobility of the reacting Cd2+ and Fe3+ cations of CdO and Fe2O3 involved in CdFe2O4 formation.