Comparison of barium peroxide, Ba(OH)(2) and Ba(NO3)(2) as the precursor of BaO for the preparation of NO (x) -storage BaO/Al2O3 material was carried out. The as prepared materials were calcined at 550 and 800 A degrees C and characterized by N-2 physisorption, XRD, Raman and FT-IR spectroscopy. Measurements of the NO (x) storage performances of these BaO/Al2O3 materials by NO2 adsorption and NO (x) -TPD experiments showed that the use of barium peroxide as the precursor of BaO inhibited the formation of BaAl2O4 and led to remarkable improvements in the thermal stability as well as NO (x) storage capacity of the final BaO/Al2O3 material calcined at 800 A degrees C.