February 2001 Ž . Materials Letters 47 2001 205–211 www.elsevier.comrlocatermatlet The densification and morphology of cordierite-based glass-ceramics Sen Mei, Juan Yang, Jose M.F. Ferreira ) ´ Department of Ceramics and Glass Engineering, UIMC, UniÕersity of AÕeiro, 3810-193 AÕeiro, Portugal Received 17 April 2000; received in revised form 29 June 2000; accepted 30 June 2000 Abstract Ž . In this study, five different proportion of a borosilicate glass from 30 to 70 wt.% were added to stoichiometric cordierite to improve the densification behaviour of cordierite-based glass-ceramica. The phase and microstructural evolution of the samples were characterised by DTA and SEM. The results show that glass content plays an important role in the sintering of Ž . cordierite-based glass-ceramics. The sintered density increases as the glass content increases at low temperature 9508C . At high temperatures, the sintered density passes through a maximum value when the glass content is about 60 wt.%, followed by a decrease as the glass content further increases. DTA results show that densification is a non-reactive liquid phase sintering process. The microstructural evolution of the samples is in good agreement with the measurements of sintered densities. At the lower glass content, the sample shows more pores and a non-uniform pore size distribution. With the glass content increasing, the pore size becomes more uniform and sintered density increases. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Microstructure evolution; Densification factor; Cordierite; Glass-ceramics; Pore distribution 1. Introduction Recently, cordierite and cordierite-based glass- ceramics attracted much attention because ordinary ceramics such as alumina, AIN, cannot be co-fired Ž . with copper at low temperatures below 10008C w x 1–3 . However, cordierite is difficult to sinter with- out sintering aids. Its optimum sintering temperature range is close to the melting point of the cordierite. Moreover, the relatively poor mechanical properties wx have prevented its widespread applications 4. ) Corresponding author. Tel.: q 351-234-370242; fax: q 351- 234-425300. Ž . E-mail address: jmf@cv.ua.pt J.M.F. Ferreira . Therefore, attention has been focused on glasses that wx promote a liquid-sintering process 5 . Addition of some sintering aids would result in the deterioration of the properties, such as large thermal expansion, higher dielectric constant. It is desirable to introduce one kind of glass into the stoichiometric cordierite to decrease sintering tem- peratures and to improve density without deteriorat- ing its properties. wx Recently, it has been reported 6 that the borosili- cate glass could be mixed with cordierite powder to promote densification. The result showed that the sintering behaviour could be represented predomi- nantly by a non-reactive liquid phase sintering and that densification was achieved mainly in the initial 00167-577Xr01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0167-577X 00 00236-6