In order to produce housings for high-temperature applications, alumina is a highly advantageous material because it has a high chemical durability and withstands high temperatures. If alumina is to be sealed, materials are necessary which have an adapted coefficient of thermal expansion (8.6 x 10(-6) K-1). If temperature-sensitive components have to be encapsulated, a rapid laser sealing process is highly advantageous. This process requires a glass which can rapidly be crystallized. In this paper, a glass powder with the composition 4.2 MgO center dot 5.0 ZnO center dot 44.1 center dot CaO center dot 26.7 Al2O3 center dot 20.0 SiO2 was sintered and subsequently crystallized using a CO2-laser. As crystalline phases, predominantly a solid solution of akermanite and gehlenite (AGSS) was formed and as phases with minor concentrations Al2O3, spinel/gahnite solid solution and ZnO. The AGSS grains have sizes of approximately 5 mu m, and Mg and Zn are enriched at the grain boundaries. After sealing at temperatures of 985 and 1135 degrees C, a similar microstructure and similar grain sizes were observed. The AGSS seems to nucleate at the glass/Al2O3 interface but also in the bulk. The AGSS and all other phases do not show a preferred orientation. The resulting coefficients of thermal expansion fit well to that of Al2O3.