Synthesis and calcinations effects on size analysis of Co3O4 nanospheres and their superparamagnetic behaviors

Abstract

Co 3 O 4 nanoparticles were synthesized by microwave process using citric acid as a capping agent. Interestingly, when calcination temperature is increased to 600 °C, nanoparticles were formed into nanospheres of about less than 20 nm observed from SEM images. The particles were aggregated into bigger size of about 65 nm when the calcination temperature was increased to 800 °C. The samples calcined at 400 °C and 800 °C show superparamagnetism above the blocking temperature and the existence of small ferromagnetism is observed when T < T b . At 600 °C, sphere like Co 3 O 4 particles exhibit complete super paramagnetism from 5 K to 300 K. These results indicated that the structural, optical and magnetic properties may be tuned by choosing appropriate calcination temperature of the sample. • Spinel Co 3 O 4 nanoparticles are synthesized by fast and effective microwave route. • Tuning of size and morphology of Co 3 O 4 was investigated by calcination temperatures. • Well defined sphere morphology was achieved for the calcinations of 600 °C. • The prepared Co 3 O 4 was modified into moderate size of less than 20 nm for 600 °C. • The 600 °C calcined sample completely obeys superparamagnetism nature from 5K–300K.