Study On Preparation And Microstructure Of La～(3+)-doping BaTiO₃ And Mn-Zn Ferrite Nano Radar Absorbing Materials

Barium titanate and Mn-Zn ferrite are traditional radar absorbing materials. They have been used widely in microwave absorber coating field because of theirs superior performance. Especially, they are characteristic of simple preparation technics and low prices. But, they also have lots of disadvantages, for example, the narrow absorption frequency band and the low absorption intensity. Rare earth doping can change their microstructure and electromagnetic parameters so that their microwave absorption capability could be advanced.The two characteristics of microwave absorber coating with excellent performance are discussed. Firstly, for reducing the reflection of electromagnetic wave on absorber coating surface, the relative complex magnetic conductivity( μ_r) of material should approximately equal to its relative complex dielectric constant(ε_r). Secondly, for enhancing the loss of electromagnetic wave within the absorber coating, theimaginary part of relative complex magnetic conductivity( μ_r'' ) and the imaginarypart of relative complex dielectric constant( ε_r'' ) of absorber coating must be increased. In addition, to enhance the capability of microwave absorption, the two conditions must be taken into account simultaneously.Ba_1-xLa_xTiO₃(x=0.0, 0.1, 0.2, 0.3, 0.4mol%) nanocrystalline was prepared by Sol-gel processes. The results of TG-DTA, FT-IR, XRD and TEM showed that BaTiO₃ nanocrystalline with cubic perovskite structure had formed at 700℃ calcined for 2h. La³⁺-doping could promote the forming of BaTiO₃ nanocrystalline, and reduce the calcining temperature. Within 0.1≤x≤0.4mol%, not only impurity did not form but also the cubic structure was not been transformed. Because La³⁺ with shorter radius replaced Ba²⁺ with longer radius, the aberrance of crystal lattices occurred so that the lattice parameter and average grain size declined with La³⁺-doping quantity increasing.Mn_0.5Zn_0.5La_xFe_2-xO₄(x=0.0, 1.0, 2.0, 3.0, 4.0mol%) nanocrystalline was prepared by Sol-gel auto-combustion processes. TG-DTA, FT-IR, XRD and TEM analysis indicated that auto-combustion powder was Mn-Zn ferrite nanocrystalline with cubic spinel structure. The impurity of Fe₂O₃ had formed after the auto-combustion powder being calcined, and the quantity of impurity manifolded with...