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

Glow discharge mass spectrometry has been used to study redox equilibr ia reactions of lanthanum and lanthanum oxide in an argon glow dischar ge. Introduction of the primary reagents of La and LaO is by sputter e jection from a cathodic sample. The plasma chemistry is greatly affect ed by oxidizing and reducing agents in the plasma, most prominent of w hich is residual water, shown here to reduce greatly the La/LaO ratio even at trace levels of water vapor. The injection of controlled amoun ts 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 s amples. O-18-enriched water was also used to follow oxidation processe s in the plasma. Attempts were made to differentiate between oxygen re actants arising from sputtered oxide sample and those originating in t he injected water.