Abstract
D. c. arc excitation method in a controlled atmosphere was applied successfully to the spectrographic determination of small amounts of 14 rare earths and 12 non-rare earth metallic elements in yttrium oxide.
In order to establish the optimum conditions, studies were made on the effects of argon to oxygen mixing ratio in the atmosphere, the selection of analytical line pairs and the effect of ignition temperature of yttrium oxalate.
Base material(6-nines) was purified by cation-exchange technique by use of EDTA as eluent, then by homogenious precipitation method with diethyl oxalate.
The intensities of the CN band spectra and the background could be remarkably reduced by the use of argon-oxygen(4 : 1) mixed gas atmosphere and it was possible to obtain the analytical sensitivities several times stronger than in the excitation in air.
Spectrographic conditions were as follows: Shimadzu Ebert type spectrograph (GE-340); amounts of sample about 30 mg (Y2O3 15mg + graphite powder 15 mg);excitation voltage 250V; arc current 10 amp.; slit width 20 μ; and duration of exposure 3 min.
The lower limits for the determination of the impurities were: 0.010.1 ppm for Yb, Mg, Al, Si, Ca, Mn, Fe, Ni and Cu; 0.11 ppm for Eu, Er, Tm, V, Cr, Sn and Pb; 1?10 ppm for La, Pr, Nd, Gd, Tb, Dy, Ho and Lu; and 20 ppm for Ce (as oxides, respectively).Coefficients of variation were 4.58.0% for rare earth impurities 5.515.9% for non-rare earth metallic impurities.
