Preparation And Characterization Of Cordierite Ceramic Sheets Obtained By Aqueous Tape Casting Process

High frequency, miniaturization, integration, and high reliability are the developing trends of novel electronic information function ceramic materials. Because of its low coefficient of thermal expansion, dielectric constant and dielectric loss,α-cordierite material has gained a significant attention in the preparation of high performance and miniaturization multilayer components, chip inductor and other electronic components.Tape casting is the most efficient and reliable method to produce thin ceramic tapes that are necessary for manufacturing multilayer microwave ceramics. Because of the heavily polluted and high cost of tradition tape casting method, the study of aqueous tape casting method with the characteristic of low cost and environment friendly is becoming the trend.The research purposes of this paper is the preparation of cordierite ceramic sheets which are obtained by water-based tape casting method. Based on a lot of experiments, the performance of cordierite powder obtained by sol-gel method is analyzed firstly;Contrast the dispersion effect of different dispersants, it takes sodium polyacrylate as dispersant in this paper and discuss the dispersing mechanism of it;then the best quality scale of the additives is discussed;after tape casting and drying process, the characterization of cordierite sheets are analysed.The study results show that the particle size distribution of cordierite powder obtained by sol-gel method is wide. The mean grain size is 2.904μm; D(0.5)=3.936μm; the specific surface area is 2.07m2/g. After ball milling 4h, the cordierite powder can disperse well.The dispersant(sodium polyacrylate) has good dispersion ability by electrostatic forcing and steric hindrance effect to the cordierite ceramic slurry; and its adsorption configuration changed with the increase of pH(form flexing and twine to stretch and expand status). The sodium polyacrylate interact with the Mg-O group and has the best dispersibility under alkaline condition(pH=9~10), and this adsorption include physical and chemical adsorption. the content ratio of plasticizer and binder (R) not only influence the properties of the cordierite water-based tape casting slurry, but also has a significant effect on the properties of cordierite tape casting sheet. The shear thinning characteristic of the slurry is helpful for the tape casting process. The optimization scheme of the slurry is as follow: the solid content is (20-30)wt%, the dispersant(PAAS) content (0.8-1.5wt)%, the binder (PVA) content is (2.0-2.6)wt%, the plasticizer (PEG) content is (1.4-2.0)wt%, the rest are deionized water and other additives.The drying process of cordierite sheets can be divided into constant speed drying stage and falling speed drying stage. The main defects of the sheets appear in falling speed drying stage. The sheets with prefect surface, good flexibility and high density are obtained when the drying temperature is 25℃.Cordierite green tapes with homogeneous microstructure and no density gradient of the Z axis direction are observed. The "peak" and "valley" structure of the sheets surface could be beneficial to the laminated construction between layers. The two crystallization peak at 968.4℃and 1003℃correspond to the precipitated phase ofμ-cordierite andα-cordierite, respectively. When sintered at 1000℃,the crystal composition and crystal content of the sintered sample don't change with the soaking time. The sintered sample has a highest sintered density at this temperature, and its dielectric performance can meet the requirements of low dielectric constant and low dielectric losses.