Lanthanum monoaluminate (LaAlO3) nanoparticles have been synthesized using microreactors made of poly(oxyethylene) nonylphenyl ether (Igepal CO-520)/water/cyclohexane microemulsions. The control of particle size was achieved by varying the water-to-surfactant molar ratio. The synthesized and calcined powders were characterized by thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron Microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Differential thermal analysis showed that LaAlO3 phase transformation decreases with increase in water/surfactant (R) value. Pure LaAlO3 phase was synthesized by annealing at 800 C for 2 h in air directly from amorphous precursors, without formation of intermediate phase. The average particle size was found to increase with increase in water-to-surfactant ratio (R). FTIR analysis was carried to monitor the elimination of residual oil and surfactant phases from the microemulsion-derived precursor and calcined powder. (C) 2009 Elsevier B.V. All rights reserved.