Characteristics of Co 3 O 4 and cobalt nanostructured microspheres: morphology, structure, reduction process, and magnetic properties

•The metal cobalt samples consist in both α-Со with a hexagonal close-packed lattice and β-Со face-centered cubic crystal at reduction temperatures 220, 240, 300 and 350°C.•Co3O4 reduction proceeded in successive stages: water removal, residual salt removal, Co3O4→CoO and CoO→Co transitions.•Inheritance of morphology may have droplet–Co3O4–Co association.