The crystallization of bismuth substituted yttrium iron garnet (Bi-YIG) powder and thin film prepared by the metal-organic decomposition method (MOD) have been studied. In the powder analysis, it was observed that the pyrolysis of metal-organic compounds begins at 250 degrees C and completed at 450 degrees C from the thermo-gravimetric-differential thermal analysis experiment. The crystallization temperature of Bi-YIG powder was 900 degrees C, and at lower temperature, secondary YFeO(3), gamma-Fe(2)O(3), alpha-Fe(2)O(3), and BiFeO(3) phases were observed by X-ray diffraction and Fourier transform infrared spectroscope. This crystallization temperature is higher than other chemical solution decomposition methods, so we suggest that the formation of BiFeO(3) in the MOD method increases the crystallization temperature. In the thin film analysis, the crystallization temperature for Bi-YIG is 750 degrees C, and at lower temperature, secondary phases are observed by X-ray diffraction. It is observed that high pre-annealing temperature promotes the crystallization of secondary phases. From the magneto-optical measurement, it was observed that the secondary phases strongly degrade the magneto-optical properties of the Bi-YIG thin film. (C) 2011 Elsevier B.V. All rights reserved.