Abstract: The nanocrystalline yttrium iron garnet and chromium (Cr³⁺) substituted yttrium iron garnet Y₃Fe_5-xCr_xO₁₂ (x=0.00, 0.20 and 0.40) ceramics was prepared by citric acid assisted sol-gel auto combustion. The produced phases were characterized by X-ray diffraction (XRD). Particles of uniform size around 74–93 nm were obtained in the cubic structure of the prepared samples. Various structural parameters such as lattice constant (a), X-ray density (d_x), unit cell volume (V) etc. were calculated from the XRD data. The variation of these structural parameters in chromium composition has been studied. The lattice constant decreases while X-ray density increases with increasing Cr content x. The morphology revealed by scanning electron microscopy (SEM) images suggests the fluffy, porous and mud like structure. It is also observed that the grain of spherical shape with somewhat agglomerations. The agglomeration can be attributed to the magnetic interactions and high surface energy of prepared nanoparticles. FTIR spectra show typical absorption bands indicating the formation of garnet structure of the samples. Upon chromium substitution, absorption bands broadened and shifted towards lower wavenumber.

Keywords: Garnet, XRD, FTIR. sol-gel auto combustion.