Research On Low Temperature Sintering And Properties Of Microwave Communication Ceramic Materials Based On CaMgGe₂O₆

5G communication is characterized by multiple connections,low latency and high bandwidth.In 5G communication,as the operating frequency of communication devices is extended to millimeter wave band,signal delay and bandwidth issues become the focus of attention.Microwave dielectric ceramics with low relative permittivity（εr<15）and high quality factor need to be actively explored to meet the application requirements.In general,electromagnetic waves with shorter wavelengths have higher frequencies and are more likely to be distorted in the propagation medium.This requires materials with low dielectric constant to support high signal propagation speed and minimize cross-coupling between the substrate and conductor;at the same time,dielectric materials have low dielectric loss,improving the operating frequency selectivity and durability.In addition,materials with low dielectric constants typically have higher quality factors,which makes them potentially useful for high-frequency signal propagation.CaMgGe₂O₆ ceramics have a low dielectric constant（εr=7.96）and are well suited for use in millimeter-wave communications and as a substrate material for microwave integrated circuits,thus attracting extensive research at home and abroad.However,its low quality factor,negative frequency temperature coefficient（τf≈-46.6 ppm/°C）and high sintering temperature（S_T=1300℃）will hinder the further application of CaMgGe₂O₆ ceramics in microwave field.In this paper,under the premise that the dielectric constant of CaMgGe₂O₆ ceramics is maintained within a certain range,Zn²⁺and Cu²⁺ions are used to replace Mg²⁺thereby improving the Q×f value of ceramics and lowering the sintering temperature;the sintering aid B₂O₃ is doped to achieve low-temperature sintering of ceramics.1.Ceramic samples were prepared by solid-phase sintering method with Zn²⁺and Cu²⁺replacing Mg²⁺in CaMgGe₂O₆ ceramics,and the effects of the two cations in the system on the composition of ceramic phases,surface morphology,crystal structure and microwave dielectric properties were investigated.The experimental results showed that in the specified range,stable solid solutions were formed with increasing substitution concentrations,and no second phase was generated.εr was mainly affected by the ion polarization rate and density,and the increase or decrease of Q×f values mainly depended on the relative density and temperature of the ceramics and the concentration of the doped substitution.τf all continued to move in the negative direction with increasing substitution.In our experiments,Ca Mg_1-xZn_xGe₂O₆ ceramics sintered at 1290℃with Zn²⁺doping of x=0.2 have the best microwave dielectric properties.The dielectric constantεr,quality factor Q×f and resonant frequency temperature coefficientτf are 7.88,64976 GHz and-36.9 ppm/°C,respectively.Ca Mg_1-xCu_xGe₂O₆ ceramics sintered at 1200℃with Cu²⁺doping of x=0.03 have the best microwave dielectric properties.The dielectric constantεr,quality factor Q×f and resonant frequency temperature coefficientτf of the ceramics are 7.32,25264 GHz and-31.4 ppm/°C,respectively.2.The sintering temperature of CaMgGe₂O₆ ceramics can be adjusted by adding sintering aids.the addition of appropriate amount of B₂O₃ to the CaMgGe₂O₆ ceramic system changes the ceramic phase composition,surface morphology and microwave dielectric properties.The XRD analysis shows that the ceramics contain both CaMgGe₂O₆ crystalline phase and B₂O₃ crystalline phase,and the apparent density and dielectric constant of CaMgGe₂O₆-B₂O₃ ceramics keep increasing with the increase of B₂O₃ concentration.The CaMgGe₂O₆ ceramics sintered at 930℃with 13%B₂O₃ have the best microwave dielectric properties in our experiment.The dielectric constanεr,the quality factor Q×f,and the resonant frequency temperature coefficientτf of the ceramics are 7.62,30014 GHz,and-39.9ppm/°C,respectively.3.Finally,CaMgGe₂O₆ ceramics with 13 wt.%B₂O₃ sintering additive and sintered at930℃were found to be suitable LTCC substrate materials,and an LTCC bandpass filter was designed.The simulated performance of the filter is center frequency 2.5GHz,bandwidth150Mhz,passband interpolation loss less than 0.2d B,return loss more than 20d B,and out-of-band rejection less than 40d B at less than 2.2GHz or more than 2.8GHz.