The present work represents, the Yttrium doped Mg1-x Cdx Yy Fe2-y O4 (where x = 0, 0.2, 0.4, 0.6 and y = 0, 0.075) synthesized using sol-gel autocombustion method. The investigation of structural and optical properties was carried out for the synthesized samples using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Ultraviolet visible spectrophotometer (UV-Vis). XRD revealed that the structure of these nanoparticles is spinel with average grain size lies in the range between 17.79 to 24.2 nm. Lattice parameter was found to increases with Mg-Cd concentration and this may be due to the larger ionic radius of the Y3+ ion. FTIR spectroscopy confirmed the formation of spinel ferrite and showed the characteristics absorption bands around 477, 558, 1060, 1381, 1628, 1707, 2918, 3433 and 3841 cm-1 . The energy band gap was calculated for samples with different ratio and average band gap energy was found to be 4.2851 eV. The substitution was resulted in slight increased in the lattice constant and that sequentially may lead to the slightly increased in the energy gap. Also found that it is in the range of semiconductor materials.
