Low-temperature Sintering Process And Application Research Of Ba₅Nb₄O₁₅ Microwave Dielectric Ceramics

The preparation of electronic components by LTCC technology can realize theminiaturization and integration of the device, the research of microwave dielectricceramics which can be sintered at low temperature is a research hotspot in the field offunctional ceramics. Due to its good dielectric properties Ba₅Nb₄O₁₅microwavedielectric ceramic was widely studied. The low temperature sintering process of solidphase synthesis was systematically investigated in this paper by researching the effectsof presintering temperature, ball grinding process, additives on the performance ofBa₅Nb₄O₁₅ceramic. EBG antenna placodewas prepared through LTCC technology atthe same time, the application prospect of Ba₅Nb₄O₁₅ceramics in the field of LTCC wasexplored by researching the process of sintering with silver electrode and simulationanalysis.The comparison of different properties of Ba₅Nb₄O₁₅ceramics which waspresintered in700¹100℃was made in the research,the results show that the rawmaterial powder all can generate Ba₅Nb₄O₁₅phasethrough presintering in700¹100℃.With the increasing of presintering temperature, powder particle size increased and Q×fvalue ofceramic increased; However, high presintering temperature made ceramicagglomerated and was adverse to ball milling. Ba₅Nb₄O₁₅ceramic with presinteringtemperature of1000℃exhibited good dielectric properties.By measuring the size of rawmaterial powder which was milled under different conditions, excellent parameters ofball grinding process could be obtained. The results showed that various shape ofgrinding ball could significantly improve the efficiency of ball milling, and millingefficiency would be decreased along with the increase of milling time. The profitabletime of ball milling is48hours. CuO, CaCO₃and B₂O₃were added to Ba₅Nb₄O₁₅ceramics when the ceramics were sintered at low temperature. The experiment resultsindicated that he optimum content of B₂O₃is0.8wt%and the appropriate additive CuOcontent is1.1wt%in the range of0.2wt%¹.1wt%. Further researches on B₂O₃-CuOsystem additives showed that5B₂O₃-2CuO and B₂O₃-CuO could make ceramicssintered at900℃and the ceramics behaved excellent performance of Q×f value. Thecomposite ceramics （1-x）Ba₅Nb₄O_15-xBaNb₂O₆were prepared by changing the ratio ofthe raw material. In the composite ceramics, the relative dielectric constant and the density decreased cause to the decreasing of x, but the Q×fand τfvalue increasedgradually at the same time. The composite ceramics exhibited excellent microwavedielectric properties of εr=41.23, Q×f=21500GHz andτf=6.2×10-6℃-1when x=0.1. Theconclusion could be obtained from the experiment of（1-x）Ba₅Nb₄O_15-xBaNb₂O₆microwave dielectric ceramics and Ag electrode that theceramics which was expected as a kind of excellent low temperature material had goodcompatibility with Ag electrode.Antenna substrates of EBG structure were prepared by means of LTCC technology,and the band gap of the EBG structure was tested. Analogue simulation for antennasubstrates of EBG structurewas carried out by HFSS software and set model material asthe composite ceramics material and LTCC slurrymaterialrespectively, simulated resultindicated that the working frequency of antenna substrates model with the compositeceramics material was slower then the frequency of LTCC slurrymaterial, andmicrowave dielectric ceramics were expected to decrease the size of the LTCCdevicewhen the working frequency was fixed.