Effect of Solvothermal Reaction-Time on Microstructure and Microwave Absorption Properties of Cobalt Ferrite

Cobalt ferrite is synthesized via a simple solvothermal method. Then, the effect of the degree of cobalt-ferrite growth on its morphology, structure, electromagnetic performance, and microwave absorption is studied as a function of the solvothermal reaction time. When the reaction time during synthesis is 8 h, the structure of cobalt ferrite is hollow spheres. In addition, when the reaction time is 12 h and 16 h, it becomes a submicron sphere with a diameter of 100-150 nm. With the increase of reaction time, cobalt ferrite underwent the process of cobalt ferrite formation, hollow structure formation, hollow structure disappearance, agglomeration separation and reagglomeration in 4-16 h. In general, CoFe₂O₄-8h shows better microwave absorption-the effective absorption bandwidth is 9.84 GHz (6-15.84 GHz) for a thickness of 1.72-3.72 mm. This represents a minimum return loss of -47.24 dB. A better understanding of both the synthesis parameters and the relationship between structure and electromagnetic properties can open new possibilities for applications and the development of microwave absorbing materials.