Research On Aqueous Tape Casting Technology And Properties Of CSLST Microwave Dielectric Ceramic

In the recent years, with the rapid development of the microwave communication technology, using the microwave dielectric ceramics material on Low Temperature Co-fired Ceramics (LTCC) has become a focus and direction. In this thesis, the (Caig/19Sri/19)0.2(Li0.5Sm0.5)0.8TiO3 (CSLST) microwave dielectric ceramics material with high dielectric constant was selected as the research objects. The sintering temperature of this ceramic was reduced by changing the partical size, while the sintering aid B2O3-CuO-LiCO3 (BCD was used as sintering additive.Then aqueous tape casting of CSLST ceramic with BCL powder was researched. The sintering behavior of the green tape co-fired with electrode Ag was investigated. The CSLST ceramics green tape for LTCC applications was obtained.The low-temperature sintering properties of CSLST microwave dielectric ceramics were researched by using sintering aid BCL and changing the partical size. The result show that when the CSLST with 2wt% BCL powder particles size was distributed between 0.1-0.4 μm,d50 was 0.170 μm and specific surface areas was 35.2 m2/g, the ceramic sintered at 875℃ for 5h. The microwave dielectric properties was:εr= 81.3, Qxf=1886GHz,τf=-27.6×10-6℃.Aqueous tape casting of CSLST microwave dielectric ceramic powder with sintering aid BCL was researched by using styrene-acrylic latex as blinder, PAA as dispersant, glycerol as plasticizer, and deionized water as dispersion medium. Suitable slurry for aqueous tape casting was obtained by researching the effect of the pH value, solid content and different amount of additives on the rheological properties of the slurry. The ingredient was adjusting pH value to 10,62.5-66.6 wt% solid content, dispersant lwt%, blinder 10-14 wt%, and the ratio of plasticizer vs. blinder was 0.25. The slurry was the shear-thinning characteristics and has not thixotropic response. The bubble in the slurry was excluded by using vacuum defoaming machine and n-butyl alcohol as the defrother. The well uniform green tape without crazing was achieved after drying at 40-60℃.The firing system was obtained after TG/DTA analysis.The diaphragm laminated later sintering at 875℃ has preferable microwave dielectric properties:er=75.8,Q×f= 1422GHz,τr-13.39×10-6/℃. The effect of CSLST with different content BCL aqueous green tape co-fired with electrode Ag was researched, sintering aid BCL would react with Ag at high temperature.When the CSLST microwave dielectric ceramics with 2 wt% sintering aid BCL aqueous green tape co-fired with Ag at 875 ℃, the shrink rate of Ag line was only 10%。Based on the research of the low-temperature sintering and aqueous tape casting of CSLST ceramics, a series of the microwave dielectric ceramics with the excellent dielectric properties and aqueous green tape would be achieved, which meet LTCC technology.