Filled glass–ceramic composites, like low‐temperature co‐fired ceramics (LTCC), must densify at temperatures <900°C. The densification mechanism of LTCC is often described by liquid‐phase sintering. The results of this paper clearly show that densification of ceramic‐filled glass–composites with a glass content above 60 wt% can be attributed to viscous sintering, which is decisively controlled by the viscosity of the glass during the heat treatment. This is demonstrated by the experimental determination of the viscosity of a MgO–Al2O3–B2O3–SiO2 glass dependent on temperature, by investigation of the wetting behavior of the glass on the ceramic filler mullite, and of the microstructural development. It was found that the glass does not wet the filler material in a temperature range up to 1000°C. Therefore, liquid‐phase sintering can be excluded. Independent of any wetting effect and therefore in the absence of capillary forces, densification starts at a temperature of 750°C, which corresponds to a viscosity of 109.5 dPa·s. This densification can be attributed to viscous flow of the glass matrix composite.
Glass–ceramic composites like low‐temperature cofired ceramics are densified at temperatures below 900°C via liquid‐phase sintering. For high‐frequency applications, materials with low dielectric losses are needed. At these frequencies glass exhibits higher dielectric losses than a crystalline phase; therefore, the glass amount is reduced after densification by crystallization. To perform a quantitative X‐ray analysis of such glass–ceramic composites, a method based on Rietveld refinement was developed. For optimum results, the X‐ray diffraction patterns were fitted using the software TOPAS 2.1 from Bruker AXS. With this method, it is possible to determine quantitatively the amount of crystalline phases and also the amount of the remaining amorphous phase.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.