In this study, Al 18 B 4 O 33 aluminum borate is synthesized by the sol-gel, precipitation, and combustion methods, which use similar starting materials. Simultaneous thermal analyzer and Fourier transform infrared spectroscopy are employed to determine the thermal behavior and the chemical bonding structures. In addition, the crystal structure and microstructure are identified by X-ray diffraction and scanning electron microscope. The results reveal that Al 18 B 4 O 33 nanorods are produced by sol-gel method and citric acid controls the morphology of powders. Additionally, Al 18 B 4 O 33 phase is obtained by decomposing Al 4 B 2 O 9 unstable phase at 1000°C by sol-gel method. However, Al 18 B 4 O 33 phase is immediately obtained from calcination of an amorphous phase at 1000°C by precipitation and combustion methods. K E Y W O R D S aluminum borates, combustion, precipitation, sol-gel, STA (TG-DTA) How to cite this article: Maghsoodi F, Naghizadeh R. Characterization of Al 18 B 4 O 33 ceramic synthesized by the sol-gel, precipitation, and combustion methods. Int J