The Aluminum-Rich Part of the System BaO–Al2O3–MgO: I: Phase Relationships

✍ Scribed by M. Göbbels; S. Kimura; E. Woermann

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 251 KB
• Volume: 136
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7676

✦ Synopsis

The subsolidus phase relations in the Al-rich part of the system BaO-Al 2 O 3 -MgO at 1800°C in air have been determined. The hexaaluminate phases in this part of the system all exhibit -alumina structure types. In the binary system BaO-Al 2 O 3 , the phases Ba 1.21 Al 11 O 17.71 and Ba 0.75 Al 11 O 17.25 were confirmed. In the ternary system, two solid solution series, BAM-I and BAM-II, exist. The solid solution range of BAM-I between the defect-free -alumina end member BaMgAl 10 O 17 and the Mg-free end member Ba 0.75 Al 11 O 17.25 can be described by the formula Ba 1؊x/4 Mg 1؊x Al 10؉x O 17؉x/4 (04x41). The solid solution series BAM-II contains higher Mg concentrations. It can be expressed by the formula Ba 2 Mg 6؊3y Al 28؉2y ) y O 50 (O4y40.

3). The Mgrich end member of BAM-II is plotted exactly at the join between the defect-free end member of BAM-I and the stoichiometric Mg-Al-spinel. Thus it is concluded that the structure of BAM-II is a mixed-layer model containing both structure units.