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The effect of CaO-B2O3-SiO2 glass on the densification, microstructure and microwave dielectric properties of Ba4Nd9.33Ti18O54 ceramics was investigated in this work. It was found that the addition of a few amount of glass (≤2%) could effectively decrease the sintering temperature owing to the viscous sintering. However, locally porous structures were formed when overmuch glass was added because of enwrapped air bubbles and rapid grain growth. In addition, the amount of remaining glass after sintering could be decreased due to the re-crystallization of CaO-B2O3-SiO2 glass. Sol-gel derived Ba4Nd9.33Ti18O54 ceramics containing 2 wt% glass can be well densified at 950°C and exhibit good microwave dielectric properties of εr=68 and Q×f=7400 GHz.

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LTCC films constrained by rigid substrate were sintered at different temperatures ranging from 760 °C to 800 °C. An optical dilatometer together with a rocking arm was employed to record sintering strains of the constrained films during the sintering process. The densification behavior of constrained films was systematically studied through the measured sintering strains by comparing with that of freely sintered films. For the constrained films, the final density was smaller and the activation energy for the densification was larger than that of the freely sintered ones. Moreover, anisotropic microstructure was induced by the tensile stress.