莫来石基板陶瓷的组成对结构与性能的影响

THE EFFECTS OF CHEMICAL COMPOSITION ONMICROSTRUCTUREAND PROPERTIES OF MULLITE SUBSTRATE CERAMICS

研究了ＭｇＯ－Ａｌ＿２Ｏ＿３－ＳｉＯ＿２系和ＢａＯ－ＭｇＯ－Ａｌ＿２Ｏ＿３－ＳｉＯ＿２系添加物的组成对莫来石电子基板陶瓷结构与性能的影响。莫来石含量（质量，下同）为７０％到９０％，样品经１５５０～１６００℃烧成。结果表明：莫来石－富硅玻璃系样品有效低的介电常数ε，但介质损耗ｔｇδ偏高。莫来石－堇青石系ｔｇδ较小，莫来石含量超过８０％的样品的抗弯强度大于２００ＭＰａ。随着添加组分含量的提高，热膨胀系数α趋于降低，莫来石含量为７５％，α（ＲＴ～２００℃）接近４．０×１０－６／℃。实验发现，ＢａＯ不仅具有显著改善ｔｇδ的作用，而且对于促进致密化和提高力学性能也有一定的贡献。引入少量的ＢａＣＯ３（１％）可使莫来石－富硅玻璃系ｔｇδ下降３０％～４０％。莫来石－堇青石系中引入一定量的ＢａＣＯ＿３，可使δ和ｔｇδ分别达到６．７和１５×１０￣－４。ＸＲＤ分析揭示ＢａＯ的引入已导致少量次晶相的生成，如钡长石、刚玉和α石英。由ＳＥＭ观察到：富硅玻璃系样品显微结构中晶粒多呈粒状，而堇青石系样品中莫来石晶粒一维发育程度较为明显。

Mullite substrate ceramics containing MgO-Al_2O3-SiO_2 tri-composition additives and BaO-MgO-Al_2O_3-SiO_2 tetra-composition additive systems were fabricated and their properties and microstructure were investigated. The change of mullite contents was in the range of 70% to 90% (in mass) and the sampleswere sintered in the range of 1550℃ to 1600℃. Experimental results show that the mullite ceramics with additives of rich-silica glass possesses lower dielectric constant but slightly higher dissipation. The mullite ceramics with additives of cordierite composition possesses less dissipation. Bending strength of the samples. is greater than200 MPa when mullite content is>80% (in mass). Thermal expansion coefficient of specimens seems to decrease with the increase of additive contents. When mullite content is 75%, corresponding a value (RT￣200℃) is nearly 4. 0 ×10￣-6/℃. It is found that adoption of BaCO_3 not only causes remarkable effect in decrease of dielectricdissipation but also contributes to promotion of densification and improvement of mechanical properties to some extent. For example, only 1% of BaCO_3 can result in decrease of dissipation by 30%￣40% for rich-silica glass system. Dielectric constant and dissipation in mullite-cordierite-BaCO_3 system are 6. 7 and 15×10￣-4 respectively by adding with 5% BaCO_3 XRD analysis results indicate that small amount of second phases is produced by the adoption of BaCO_3, such as barium feldspar, corundum and a-quartz. SEM observation results show thatthe morphology of mullite ceramics with rich-silica glass additives is mostly granular and that of the ceramicswith cordierite additives has columnar character.