MASS-SPECTROMETRIC STUDY OF RARE-EARTH-OXIDE EQUILIBRIA IN THE GLOW-DISCHARGE

Glow discharge mass spectrometry has been used to study redox equilibria reactions of lanthanum and lanthanum oxide in an argon glow discharge. Introduction of the primary reagents of La and LaO is by sputter ejection from a cathodic sample. The plasma chemistry is greatly affected by oxidizing and reducing agents in the plasma, most prominent of which is residual water, shown here to reduce greatly the La/LaO ratio even at trace levels of water vapor. The injection of controlled amounts of water vapor was used to demonstrate this effect. Mixtures of Ar and Ne permitted the study of atomization changes for Ag, Ti, and La samples. O-18-enriched water was also used to follow oxidation processes in the plasma. Attempts were made to differentiate between oxygen reactants arising from sputtered oxide sample and those originating in the injected water.