Low-termperature Firing BaO-Nd₂O₃-TiO₂ Microwave Dielectric Ceramics

With the quick increasment of mobile telecommunication industry, low temperature cofirable ceramics are developed very quickly. In order to fulfil the need of LTCC design, not only the low- ε materials but also high- ε materials should be developed. Ba6-3xLn8+2xTi18O54 solution is the most important high- ε material and can be used as key materials in duplexer.In this thesis, effects of composition and sintering temperature upon the sintering characteristics, phase composition, microstructures and microwave dielectric characteristics of Ba6-3xNd8+2xTi18O54 high-ε microwave dielectric ceramics were investigated. Modification of microstructure and microwave dielectric properties were conducted by Bi substitution for Nd, add BCC, ZBS, BBS in the Ba6-3xNd8+2xTi18O54 ceramics.With increasing x of Ba6-3XNdg+2XTi18O54 ceramics(0.5 ≤ x≤ 0.8), dielectric constant decreased as a whole but at x=2/3 there was a break and got the maximum, while Q f factor increased first then decreased and at got the maximum at x=2/3.Effects of composition and sintering temperature upon the microwave dielectric characteristics of Ba6-3X(Nd1-y,Biy)8+2XTi18054(x=2/3) ceramics were investigated. With the increasing Bi content in the ceramics, sintering temperature decreased, dielectric constant increased and the Q f factor kept at a high level.Adding BCC as a sintering aid, with the increasing amount of BCC in Ba6-3XNd8+2XTi18O54, dielectric constant and Q f factor decreased, while sintering temperature decreased first then kept steady, this was close related to the high melting point.With the multiplex aids of ZBS/BCC BBS/BCC, Ba6-3xNd8+2xTi18O54 ceramics could be sintered at a low temperature, and could be cofired with Cu or Ag electrode. With invariable amount of BCC, with increasing amount of ZBS or BBS in Ba6-3xNd8+2xTi18O54, dielectric constant decreased first and then increased while the Q f factor kept a good value. When 2.5wt%BCC and 5wt%BBS were added,Ba4(Nd0.85Bi0.15)28/3Ti18O54 ceramics could be sintered at 950℃, and at 5.6GHz, ε = 60.25, Q f=2577GHz, τ f=+25.1ppm/℃Though modification of Ba6-3xNd8+2xTi18O54 and addition of multiplex sintering aids, a series of low-firing high- ε microwave dielectric ceramics used as multi-layer components can be achieved.