Preparation And Dielectric Properties Of Bi-based Vanadates Ceramics With Ultra-low Sintering Temperatures

The recent rapid advances in wireless telecommunication,Internet of Things,the tactile Internet（5th generation wireless systems）,the Industrial Internet,electronic warfare,satellite broadcasting,and intelligent transport systems demand low loss dielectric materials with ultra-low sintering temperatures with modern component fabrication techniques.The low temperature cofired ceramic（LTCC）technology is used to fabricate devices such as band pass filters,oscillators,wave guides,and antennas for miniaturization of microwave components in wireless communication.In LTCC,the green dielectric tape with passive components is cofired with the common electrode silver at temperatures less than the melting point of silver（961^oC）.Currently intensive search is going on to find materials with ultra-low firing temperatures less than 700 ^oC and the number of papers published on ULTCC is rapidly increasing.A series of microwave dielectric ceramics with ultra-low sintering temperature were prepared by conventional solid-state method,and the crystal structure and microwave dielectric properties were investigated.1.A kind of low-firing microwave dielectric ceramics NaBi₃V₂O₁₀ was prepared by the conventional solid-state method.The NaBi₃V₂O₁₀0 ceramic could be well densified at relatively low temperature 660 ^oC and exhibited promising microwave dielectric properties withε_r=26.29,Q×f=3,200 GHz,η_f=-69 ppm/^oC.Besides,it is compatible with Ag electrodes.Frequency and conductivity relaxation temperature characteristics of the NaBi₃V₂O₁₀ ceramic can be obtained after fitting by Arrhenius equation.The relaxation activation energy equals to about 0.95 eV and the conductivity activation energy equals to about 0.806 eV.The optical absorption properties of the Na₂BiZn₂V₃O₁₂ ceramic were investigated by UV-Vis techniques.The band gap energy（Eg）were calculated with a value of about 3.025 eV.2.The Na₂BiZn₂V₃O₁₂ ceramic sintered at 600 ^oC exhibited a relative permittivity（ε_r）²2.3,a quality factor（Q×f）¹9,600 GHz（at 8.6 GHz）,a temperature coefficient of resonance frequencyη_f¹5.5 ppm/^oC.The relative density showed a obvious dependence on the sintering temperature and a maximum value of96.3%at 600 ^oC.Thereafter,the relative density decreased as the sintering temperature increased,which might be due to extrinsic factors,such as the increase of pores and the abnormal grain growth.Chemical compatibility measurement indicates that both Ag and Al did not react with silver.