Double-Shelled Yolk–Shell Microspheres with Fe3O4 Cores and SnO2 Double Shells as High-Performance Microwave Absorbers

Double-shelled yolk–shell microspheres with Fe3O4 cores and SnO2 double shells have been successfully synthesized by combining the versatile sol–gel process and hydrothermal shell-by-shell deposition method. The as-synthesized double-shelled Fe3O4@SnO2 yolk–shell microspheres have uniform size, unique morphology, well-defined shells, favorable magnetization, large specific surface area, and high porosity and exhibit significantly enhanced microwave absorption properties in terms of both the maximum reflection loss value and the absorption bandwidth. The excellent microwave absorption properties of these microspheres may be attributed to the unique double-shelled yolk–shell structure and synergistic effect between the magnetic Fe3O4 cores and dielectric SnO2 shells.