Sintering Additives to Eliminate Interphases in Cordierite Ceramics

Abstract

Effects of the sintering additives CeO2 and K2O on eliminating interphases of cristobalite and spinel were studied by means of XRD, SEM/energy‐dispersive spectrometer, and TMA techniques to obtain high cordierite contents. Adding 4 wt% CeO2 significantly stimulates the conversion of cristobalite to cordierite, depresses spinel formation and yields less glassy phase. It is helpful to prepare a ceramic with a high content of cordierite and a low thermal expansion coefficient when sintered at 1400°C for 3 h. Addition of 1–2 wt% K2O results in a large amount of glassy phase and is less effective in eliminating the interphases.

Effects of CeO2 addition on the properties of cordierite-bonded porous SiC ceramics

“…The positive influence of adding CeO 2 on promoting the phase transformation towards cordierite has been reported in the previous works. [13][14][15][16][17] Therefore, CeO 2 is chosen as the sintering additive in the present work to improve the properties of cordierite-bonded porous SiC ceramics. The effects of CeO 2 addition on the fabrication and properties of cordierite-bonded porous SiC ceramics were investigated.…”

Microwave assisted sintering of in-situ cordierite foam

“…Secondary crystalline phases such as mullite, corundum, spinel, forsterite, enstatite, cristobalite are often present [3,4], together with a glassy phase and this complex final mixture determines the properties of the samples [3]. Especially, in cordierite ceramics prepared by oxide powder sintering, the cordierite phase is inevitably accompanied by the phases of cristobalite and spinel, which will increase the thermal expansion coefficient of the ceramic [4].…”

“…The additives as such result in some changes in sintering and ultimately, properties of ceramics [7]. Unfortunately, the electrical and thermal properties of cordierite are degraded by sintering aids; especially the increases of thermal expansion coefficient caused by many of these additives are remarkable [2,4,7,8].…”

“…Many sintering additives such as B 2 O 3 , P 2 O 5, Li 2 O, etc. have been tested for the cordierite ceramic for this purpose [4]. The additives as such result in some changes in sintering and ultimately, properties of ceramics [7].…”

“…Especially, in cordierite ceramics prepared by oxide powder sintering, the cordierite phase is inevitably accompanied by the phases of cristobalite and spinel, which will increase the thermal expansion coefficient of the ceramic [4]. Overfiring results in the deterioration of crystalline cordierite into forsterite and mullite, which appreciably increases the thermal expansion; underfiring fails to develop sufficient crystalline cordierite for low thermal expansion and high shock resistance [5].…”