Investigation of ceramic materials using ICP-AES with external electrothermal vaporization

The evaporation and excitation processes for several trace elements in ceramic powders are studied. The advantages of an electrothermal vaporization are the easier preparation, no dilution and a shorter experiment duration. The investigated ceramic powders consist of synthetic mixtures including the systems Al2O3-SiO2 and Al2O3-MgO. The trace elements are bound as oxides. The evaporation is monitored by 59Fe and 115Cd. Since the evaporation rates are measured in addition to line intensities, the influence of various parameters on evaporation as well as on excitation processes can be individually examined. The influence of matrix composition is determined. It is found that melting and sintering processes of the matrix are of great importance for the evaporation of trace elements. Thus the best results are obtained when trace elements evaporate below the melting temperature of the matrix. Therefore the addition of thermochemical substances is necessary for several elements of low volatility. In the case of highly volatile elements, for example Cd, additives seemed to have only a small influence on the volatilization rate. Accordingly, only the excitation is affected. For example, the evaporation rate of Cd is constant through the whole Al2O3-MgO system. The measured line intensity of Cd is also constant within a large range of MgO content. The evaporation rate and line intensity of Fe decrease linearly with MgO concentration. (author)