Study Of Mg₂(Si,Ti)O₄ System Dielectric Ceramics Sintered At Medium Temperature

In this paper, dielectric properties of Mg₂(Si,Ti)O₄ based low dielectric ceremics materies were studied systematically, such materials can be applied to the electronic circuit as the substrate materials. On the promise of not reduce the dielectric properties , how to reduce the sintering temperature is the key point.We prepared two kind of glass power which were added to Mg₂(Si_1-xTi_x)O₄ system as sintering additives using high temperature melting and sol-gel method,both of them can decrease the sintering temperature. By discussing the effects of the addition of glass and bismuth oxide with low melting and Si/Ti at B-site on microsture and dielectric properties, revealed some modified basic rules, at the same time ,Mg₂(Si,Ti)O₄ based dielectric ceremics materies with good dielectric properties sintered at medium temperature were abtained.This article also improved processing route of basic materies, the optimum process is pre-synthesized precursor of Mg2SiO4 and Mg2TiO4 calcined at 1200℃for 2h, then synthesized Mg₂(Si_1-xTi_x)O₄. Doped 2wt% of glass which prepared by high-temperature melting method to Mg₂(Si_1-xTi_x)O₄ (x = 0.05,0.1,0.¹⁵,0.2), sintered at 1200℃for 2h, the dielectric loss is in the range of 0.00012 0.0002, and with the replacement of Ti on Si at B-site increasing , dielectric constant (ε) of Mg2 (Si1-xTix)O4 ceramic increased, the dielectric constant temperature coefficient (αε) shifted for the negative growth. When Ti content (x) is 0.1, samples have the best dielectric properties at 1MHz:ε= 14.2, tanδ= 1.2×10^-4,αε= 1.7×10^-6 /℃,ρv = 4.2×10¹⁵Ω·cm. Doped 2wt% of glass powder prepared by sol - gel method , with the temperature of heat treating increasing, the activity of powder increased, the density of ceramics improved as well.Doped 2wt% of bismuth oxide, with the holding time increasing (≤6h), loss(tanδ) decreased, but the holding time increased to 8h, the loss (tanδ) increased again, samples sintered at 1280℃for 6h have the best dielectric properties:ε= 14.6, tanδ= 3.6×10^-4,αε= 9. 9×10^-6 /℃,ρv = 3.1×10¹⁵Ω·cm.