Barium ferrite BaFe12O19 hollow microspheres of low density (about 2.50 g cm(-3)) were synthesized without BaFe2O4 or other intermediate phase by spray pyrolysis technique, combined with co-precipitation precursor and followed further heat treatment. The relationships between the microstructure, magnetic properties and the sintering temperature, time were investigated. Hollow microspheres, constituted by nanometer particles, showed a broad particle distribution of 2-15 mu m. When the sample was sintered at 900 degrees C for 3 h or at 1100 degrees C for 2 h, pure BaFe12O19 ferrite was formed. With the increase of the sintering temperature or time, the grain size and preferential growth orientation were influenced, the saturation magnetization (M-s) had a small increase, and the coercive force (H-c) decreased obviously. (c) 2005 Elsevier B.V. All rights reserved.