Stoichiometric LaMnO3and LaCoO3nanoparticles were synthesized via calcination of a dried solution,containing molar ratio of La(NO3)3·6H2O/[Mn(NO3)2·4H2O or Co(NO3)2·6H2O]=1 and citric acid as disperser at temperature range of 600–900 oC for 5 h.The role of organic additive concentration,which was 0.0,1.0,2.5 and 5 times of the total number of moles of the nitrate ions,was investigated on phase formation,morphology,extent of crystallization and particle size of the products.Products were characterized by X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)analysis.The tendency of lanthanum ion toward manganese cation was observed to be more than to cobalt cation for the formation of LaBO3(B:Mn or Co)perovskite phase.A spongy product was formed on perovskite phase formation or in the presence of citric acid.A constructive or destructive effect was observed for the organic disperser on perovskite phase formation,which depended on mole of the citric acid. Stoichiometric LaMnO3and LaCoO3nanoparticles were synthesized via calcination of a dried solution, containing molar ratio of La (NO3) 3.6H2O / [Mn (NO3) 2.4H2O or Co (NO3) 2.6H2O] = 1 and citric acid as disperser at temperature range of 600-900 oC for 5 h. The role of organic additive concentration, which was 0.0, 1.0, 2.5 and 5 times of the total number of moles of the nitrate ions, was investigated on phase formation, morphology, extent of crystallization and particle size of the products. Products were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) Manganese cation was observed to be more than to cobalt cation for the formation of LaBO3 (B: Mn or Co) perovskite phase. A spongy product was formed on perovskite phase formation or in the presence of citric acid. A constructive or destructive effect was observed for the organic disperser on perovsk ite phase formation, which depended on mole of the citric acid.