Getter potentialities of some intermetallics: ZrAl 2, ZrAl 3 and CeNi 5

Abstract

The oxidation kinetics of single phases ZrAl 2, ZrAl 3 and CeNi 5 have been studied as a function of temperature and fugacity of oxygen to investigate the getter potentialities of these intermetallics. These measurements have been performed using a technique developed in our laboratory for measuring the kinetics of very low oxygen (≥10 −9 moles) consumption by a given sample. Powder samples of ZrAl 2 and ZrAl 3 were thermally cycled first at 8 ppm (0.8 Pa) of oxygen then at 90 ppm (9 Pa). Each cycle was performed with a soak at 1063 K; the results of oxygen consumption rate and the actual oxygen consumption show that ZrAl 2 has greater reactivity when compared to ZrAl 3. Furthermore, ZrAl 2 becomes reactive at lower temperatures (320°C). Small pieces of CeNi 5 were studied at 6 ppm (0.6 Pa) of oxygen. More than one isotherm was performed during each experiment to investigate the oxygen consumption of the intermetallic as a function of temperature. Oxygen consumption data and the relatively low reaction temperature (>300°C) show good potentialities as getter of this intermetallic. In particular, the decrease of the oxygen content in the gas mixture was found to be five orders of magnitude, producing a minimum oxygen partial pressure of 2×10 −6 Pa in the Ar stream for several hours.