HALOCARBON-ASSISTED SLURRY VAPORIZATION IN INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY FOR THE ANALYSIS OF SILICON-NITRIDE POWDER

A conventional Babington-type nebulizer was applied for introduction o f samples in the form of solutions and slurries (1 % m/m) produced fro m a finely dispersed silicon nitride (Si3N4) powder (mean particle siz e 0.54 mum). Calibration with solution standards for the slurry method resulted in 20-40% negative deviations in the results for impurities of Al, Fe, Ca, Mg and Ti compared with the dissolution-based analysis. The addition of Freon-12 (CCl2F2), as a possible halogenation agent, to the plasma resulted in decreased negative deviations by factors of between 1.2 and 2.8, which suggests that the degree of evaporation of the slurry particles was increased by halogenation. The fact that the negative deviations could not be completely eliminated could perhaps b e explained by a difference in the efficiency of nebulization (as the sample introduction process) for the solutions and the slurries, which applies rigorously to the present sample type and nebulizer system. W ith the introduction of Freon, no degradation in the linearity of the analytical curves was found in contrast to earlier observation by othe r workers. The line-to-background intensity ratios (wavelength > 220 n m) were not decreased at the rate of halocarbon introduction eventuall y used.