Polarization loss in rutile TiO2 doped with acceptor ions for microwave absorption

With an increase in electromagnetic (EM) pollution, inducing polarization loss using lattice defects has become one of the main strategies for the design and optimization of a new generation of microwave absorbers. In this study, point defects in TiO2 absorbers are designed and controlled using a sol-gel method. The influences of the electronegativity difference and the ionic valence states of the dopant ions on the microwave absorption (MA) performance of rutile TiO2 composites are investigated. The results show that the defects such as oxygen vacancy (V-O(center dot center dot)) and Ti3+ can be adjusted continuously at a high-temperature sintering process. Cu2+, which has a larger electronegativity than Ti4+ (Cu-chi = 1.90(2+) > Ti-chi = 1.54(4+)) promotes the localization of electrons. Furthermore, compared with Ag+, which has a similar electronegativity (Ag-chi = 1.93(+) approximate to Cu-chi = 1.90(2+)), polyvalent copper ions (Cu2+ + e -> Cu+) enhance the electron-hopping process. The formed electron-pinning defect dipole clusters (Ti-Ti ', V-O(center dot center dot), Cu-Ti '', Cu-Ti ''', Ti3+ -> V-O(center dot center dot )<- Ti3+, Ti3+ -> V-O(center dot center dot)<- Cu2+ + e, Cu2+ + e -> Cu+, Ti4+ + e -> Ti3+) produce a stronger polarization relaxation process, which regulates the MA performance of TiO2 absorbers. Therefore, this study provides an essential reference for refining the EM wave attenuation performance of simple oxide absorbers.