Controlling particle size and morphology during the synthesis of nanocrystalline powders by the spray pyrolysis (SP) technique is a major challenge. A mathematical modeling based on certain governing parameters is developed for predicting the critical nanocluster sizes and nanoparticulates being synthesized by two fluid SP technique. Correlation is established between experimentally obtained nanoparticulates, theoretically predicted cluster diameters and the surface areas of the synthesized powders of variable dimensions. The developed model is also proposed to apply as the standard for determining the particle sizes, cluster diameter and surface areas for any intermediate precursor concentration for a definite system. A novel method is adopted for growth of the particulates by adding precalcined powders (ash) as nucleation sites during the atomization process for the subsequent runs. Experimental validation of the model is established using strontium doped lanthanum manganite (LSM) of various particle dimensions as applicable for multi-functional purpose in solid oxide fuel cell cathode. (C) 2013 Elsevier B.V. All rights reserved.