The thermal transformation of Mg-P zeolite to a cordierite - mullite composite
Rüdinger, Bernd; Fischer, Reinhard X.
European Journal of Mineralogy Volume 9 Number 6 (1997), p. 1257 - 1276
published: Dec 2, 1997
manuscript accepted: Jun 18, 1997
manuscript received: Jan 23, 1997
ArtNo. ESP147050906015, Price: 29.00 €
Abstract Cordierite - mullite composites are used to produce glass ceramic substrates for microelectronic packaging. The composite material is obtained here by thermal transformation of Mg-exchanged zeolite P. The crystallization process is described for two precursor zeolites with different Mg exchange rates by quantitative Rietveld analyses and differential thermal analyses. X-ray powder diffraction experiments are performed in situ between room temperature and 1450°C as well as on the quenched samples. At about 300°C, zeolite Mg-P is rendered amorphous and crystallizes to Mg-ß-quartz and mullite above 950°C and furtheron to a pyroxene phase above 1050°C, where the amorphous component is completely exhausted. At higher temperatures, Mg-ß-quartz and pyroxene fractions decrease, accompanied by the formation of sapphirine and cristobalite. At 1250°C, 6.6 formula units Mg-ß-quartz, 9.4 mullite, 1.1 enstatite, 0.8 sapphirine, and 8.2 cristobalite coexist with the first appearence of 0.1 cordierite. Above 1250°C, sapphirine and cristobalite react to yield increased amounts of cordierite, giving 3.1 mullite, L2 cristobalite, and 7.6 cordierite at the final firing step at 1400°C. All reactions represent dynamic, non-equilibrium conditions, similar to phase formation in the ceramic sinter process. The high-temperature form of cristobalite is partly stabilized as a Mg-stuffed derivative.