OPTIMIZATION OF ELECTROTHERMAL VAPORIZATION OF IMPURITY ELEMENTS IN CERAMIC POWDERS USING INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROSCOPY

Previous investigations have shown that the combination of electrothermal vaporization (ETV) with inductively coupled plasma atomic emission spectrometry (ICP-AES) produces a promising method for the analysis of ceramic powders. The aim of the present investigation was to clarify the principal importance of the thermochemical processes in ETV-ICP-AES analysis by studying the role of chemical modifiers on the vaporization of difficult-to-vaporize carbide-forming elements in powdered ceramic material. One criterion for the choice of the chemical modifier was the thermodynamical probability of chemical reactions between SiC and the modifier. The following compounds were considered: KF; (C2F4)n; Na2B4O7; BaCO3; Ba(NO3)2; BaO; AgCl; CoF2; and Pb(BO2)2, as well as combinations of these modifiers. The temperature range of interest was 1600-2100-degrees-C. The choice of a chemical modifier was based on qualitative and quantitative investigations of the reaction products using scanning electron microscopy (SEM), energy dispersive X-ray analysis and ICP-AES. The results of thermodynamic calculations were generally found to be in agreement with the results from SEM and X-ray diffraction analyses of the compounds remaining in the crucible. The importance of the role of the chemical modifier in ETV-ICP-AES analysis was demonstrated. The complex modifier BaO + CoF2 (1:1) decomposed almost totally, allowing the impurities to be released. Using this approach the problem of total evaporation of difficult to volatilize elements from any type of powdered sample could be solved.