The Processing, Structure And Microwave-absorbing Performance Of Barium Ferrite Doped With La, K And Zn

This paper compared the microwave-absorbing performance of two different Sol-Gel processed materials, the M type barium ferrite (LaK)_xBa_1-xFe₁₂O₁₉ (x=0.3, 0.5) doped with both rare-earth metal lanthanum ions and the alkali metal potassium ions and the BaFe₁₂O₁₉ without doping. The variation of microwave absorbing performances was determined by X-ray diffraction, scanning electron microscope and network analysis. X-ray diffraction and scanning electron microscope was also used to test the ball milling processed W type BaZn-Ferrite (BaZn₂Fe₁₆O₂₇) doped with Zn at various temperatures. Its wave absorbing performance in a narrow frequency band was measured by a microwave detection system in our laboratory. The result shows that M-type Ba-Ferrite is a kind of excellent high frequency and super high frequency microwave absorbing material. Under the condition that its structure does not change, doping some certain amount of lanthanum and potassium can significantly improve its microwave absorbing performance, especially when the doping amount is at x=0.3, the specimen reaches its highest absorbing level at all frequency band. The reason could be the increased dielectric loss by doping La and K and magneto—crystalline anisotropy of BaZn-Ferrite, and the increased magnetic loss of BaZn-Ferrite as well. But When the BaZn-Ferrite is over doped, there exists the possibility of forming new impurity and thus will cause declining in its wave absorption ability.The microwave absorbing performance of another W- type Ba-Ferrite doped with Zn, i.e., Ball milling processed BaZn₂Fe₁₆O₂₇, had not been significantly improved in some certain frequency band, although the grain size had been verified to be the order of nanometer.