The ultrafine LaFeO3 with particle size of 12-75 nm was prepared by sol-gel method. In the process of gel to ultrafine powder, the wt. loss reached 90%. The lowest forming temperature of single phase crystalline LaFeO3 ultrafine powder was observed at 600? The diameter of the ultrafine powder increases significantly with increasing firing temperature It was discovered from the surface photovoltage spectroscopy that the long-distance ordered crystal structure and the integrated energy band structure are gradually formed in the internal of the particles with the increase of particle diameter The smaller of the particles, the more evident of the surface properties.

Key words: IRON OXIDE, LANTHANUM OXIDE, SOL-GEL PROCESS, ULTRAMICRON