Aqueous tape casting of microwave ceramic BaO center dot La2O3 center dot 4.7TiO(2)

An aqueous-based slip for tape-casting BaO . La2O3. 4.7TiO(2) ceramic sheet s was studied that is suitable for substrates of microwave devices. Two sep arate dispersants, Na4P2O7 (S2) and CH3(CH2)(4)SO3Na, combined with poly(vi nyl alcohol) and poly(ethylene glycol), were used as slip additives. The ze ta potential, particle size distribution, viscosity (of the slip), tensile strength and density (of green tapes), sintered density, microstructures an d microwave dielectric properties (of sintered substrates) were characteriz ed, and their dependence on the additives were analysed. S2 shows a better dispersion function and leads to a higher density of the tapes. During the sintering, the S2 liquid on grain boundaries hindered the grain growth and the formation of second phase. The dispersant-dependent microstructures of the substrates show strong influences on the dielectric properties.