Systematic study of the outgassing behavior of different ceramic materials

Abstract

The outgassing rates of various ceramic materials were systematically investigated. This paper intercompares the most relevant ceramic material classes used in vacuum technology, namely, oxide (five different types investigated) and non-oxide based ceramics, including nitrides (four different types) and carbides (three different types). For this purpose, the Outgassing Measurement Apparatus, which uses the difference method, was applied. Besides time, also, temperature dependence of outgassing was studied to check whether a previous heat treatment of the ceramics is necessary. Additionally, the outgassing species were qualitatively determined by a quadrupole mass spectrometer. In total, relatively large differences were found between the investigated ceramic materials for their initial outgassing rates as well as for their behavior at elevated temperatures. All investigated types of carbide ceramics showed very low outgassing rates of less than 3 × 10−8 Pa m3/(s m2) after 100 h at room temperature, whereas rather high outgassing rates of about 10−5 Pa m3/(s m2) were found for magnesia as well as the tested nitride ceramic types. Thus, depending on the ceramic material, a heat treatment is strongly recommended before use in ultrahigh vacuum applications.