Solid‐State Synthesis of LaCoO 3 Perovskite Nanocrystals

A solid‐state reaction process has been developed to synthesize perovskite‐type LaCoO 3 nanocrystals with grain diameters of 15–40 nm. In the first step of the preparation, ∼5 nm composite hydroxide nanoparticles are synthesized by the solid‐state reaction of La(NO 3 ) 3 · n H 2 O and Co(NO 3 ) 2 ·6H 2 O with KOH at ambient temperature. A perovskite‐type rhombohedral LaCoO 3 phase appears at 550°C, after the hydroxide has been calcined at various temperatures. The phase transformation process is complete at ∼800°C, yielding a single‐phase binary oxide. The results indicate that the new process is convenient, inexpensive, and effective for obtaining LaCoO 3 nanocrystals with high yield.