Study On Properties Of Mg₂Al₄Si₅O₁₈ Ceramic Materials Sintered At Low And Medium Temperatures

The information age has put forward higher requirements for electronic devices made of microwave dielectric ceramics:miniaturization,integration,high speed,and low latency.LTCC technology provides an effective way for the high integration and miniaturization of devices.In order to realize the co-firing of ceramics and Ag electrodes,it is of great significance to study ceramic materials that can achieve low temperature sintering and have good performance.The main research content of this paper focuses on lowering the sintering temperature of Mg₂Al₄Si₅O₁₈ ceramics to achieve low temperature sintering.The sintering temperature of Mg₂Al₄Si₅O₁₈ ceramics is lowered by doping oxide and compounding with low melting glass.In addition,the sintering kinetics of two glass/ceramic systems were studied,and the internal mechanism of low-temperature sintering was explored.Firstly,the effect of doping Yb₂O₃ on the firing reduction and performance of Mg₂Al₄Si₅O₁₈ ceramics was studied.The results show that Yb₂O₃ doping can form a low-temperature Yb₂?Si₂O₇?phase,promote the densification of Mg₂Al₄Si₅O₁₈ ceramics,and effectively reduce the sintering temperature of Mg₂Al₄Si₅O₁₈ ceramics.When 7wt%Yb₂O₃ is added,the sintering temperature is reduced from 1430?to 1330?,its dielectric properties:dielectric constant is 5.5,dielectric loss is 3.24×10^-4,temperature coefficient of resonance frequency is-24 ppm/?.Then the effects of two low-dielectric,low-melting-point glasses on Mg₂Al₄Si₅O₁₈ceramics'performance were studied.Experiments show that adding a certain amount of MBS glass can reduce the sintering temperature of Mg₂Al₄Si₅O₁₈ ceramic to 950?.Good performance can be obtained when adding 47.5wt%MBS glass:dielectric constant is 5.1,dielectric loss is 2.3×10^-3,resonance frequency temperature coefficient is-26 ppm/?,thermal expansion coefficient is 6.6 ppm/?,bending strength is 102 MPa;on the other hand,adding a certain amount of CBS glass can reduce the sintering temperature of Mg₂Al₄Si₅O₁₈ ceramic to900?.When the amount of CBS glass is 47.5wt%,the best performance can be obtained:the dielectric constant is 6.4,The dielectric loss is 4.33×10^-3,the temperature coefficient of resonance frequency is-31 ppm/?,the coefficient of thermal expansion is 8.1 ppm/?,and the bending strength is 155 MPa.Finally,two sintering activation energy calculation models based on Wang and Jenqdaw's constant heating rate model and Arrhenius equation-based constant heating rate model were used to theoretically calculate the sintering activation energy of two glass-ceramic systems.The results show that the sinter activation energy calculated by the two sintering activation energy calculation models is relatively close,but the consistency of the straight line fitted by the second model is better than that of the first model.With the increase of the content of the two glasses,the sintering activation energy of the two glass-ceramic systems calculated by the two models is continuously decreasing,which explains that MBS glass and CBS glass can reduce the sintering temperature of Mg₂Al₄Si₅O₁₈ ceramic from the internal mechanism.At the same time,when the content of MBS glass and CBS glass is also 47.5wt%,the sintering activation energy calculated using the constant heating rate model based on the Arrhenius equation is 765 kJ/mol and 436 kJ/mol,respectively,which explains that the effect of CBS glass on reducing sintering temperature is better.