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

Abstract

An aqueous-based slip for tape-casting BaO . La2O3. 4.7TiO(2) ceramic sheets was studied that is suitable for substrates of microwave devices. Two separate dispersants, Na4P2O7 (S2) and CH3(CH2)(4)SO3Na, combined with poly(vinyl alcohol) and poly(ethylene glycol), were used as slip additives. The zeta potential, particle size distribution, viscosity (of the slip), tensile strength and density (of green tapes), sintered density, microstructures and microwave dielectric properties (of sintered substrates) were characterized, 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.