The Preparation And Properties Of Bi-Layer Structure Bi₄Ti₃O₁₂ And SrBi₂Nb₂O₉ Microwave Dielectric Ceramics

In this paper,the Bi₄Ti₃O₁₂ and SrBi₂Nb₂O₉ ceramics were prepared by the conventional solid-state ceramic route and were modified by the optimization of preparation process and the ion doping.The test method used in this experiment mainly has the bulk density,XRD,SEM and network analyzer.In this paper,the Ca element was selected as the substitution for Bi site.And the structure and the microwave dielectric properties of Ca_xBi_4-xTi₃O_12-x/2 samples?x=0.0,0.6,1.0,1.2 and 1.4? were investigated.The XRD patterns of Ca_xBi_4-xTi₃O_12-x/2ceramics showed that little secondary phases was observed for x=1.4.Therefore,the solubility limit of Ca_xBi_4-xTi₃O_12-x/2 ceramics was estimated to x=1.2.With the content of Ca²⁺ions increasing,the dielectric constant ?_r and Q×f values increased at the beginning and then decreased.The optimal microwave dielectric property was obtained for the Ca_1.2Bi_2.8Ti₃O_11.4 ceramic.The effects of synthesis temperature,sintering temperature and holding time on the dielectric properties of Ca_1.2Bi_2.8Ti₃O_11.4microwave dielectric ceramics were studied.The optimal microwave dielectric property of?_r=166,Q×f=704 GHz?at 3.2 GHz?was obtained for the Ca_1.2Bi_2.8Ti₃O_11.4ceramic sintered at 1050? for 5 h.In this paper,the microstructure and the dielectric properties of Bi₄Ti₃O₁₂ were discussed by Ca²⁺,Nb⁵⁺or Mg²⁺,Nb⁵⁺ions of the same amount of doped composite and changing quantity of adding Mn.We found the quality factor of Bi₄Ti₃O₁₂ceramics is obviously improved with Mg²⁺,Nb⁵⁺composite under the condition of microwave frequency.The optimal microwave dielectric properties of?_r=113.57,Q×f=586 GHz?at 3.95 GHz?was obtained for Mg_0.1Bi_3.9Nb_0.1Ti_2.9O₁₂ ceramics sintered at 1100? for 5 h.The Mn addition could improve the dielectric properties of Bi₄Ti₃O₁₂ in the frequency of 1 MHz,but it did not improve the value of Q×f in the microwave frequency.The structure and dielectric properties of Ca_xSr_1-xBi₂Nb₂O₉?x=0.0,0.3,0.6 and1.0?were also studied by changing quantity of Ca-doped.The SEM of Ca_xSr_1-xBi₂Nb₂O₉ showed the size of the grains was found to increase with increasing x in Ca_xSr_1-xBi₂Nb₂O₉.The optimal microwave dielectric property of?_r=98,Q×f=672GHz?at 2.92 GHz?was obtained for the CaBi₂Nb₂O₉ ceramic sintered at 1050? for 5h.The effects of Mn addition on the dielectric properties of CaBi₂Nb₂O₉ ceramic were investigated.It was found that CaBi₂Nb₂O₉-0.1wt%MnCO₃ ceramic sintered at1050? for 5 h showed better dielectric electrical properties:?_r=116.71,tan?=3.48×10^-3.