Carbothermic Reduction for the Quantitative Determination of the Oxygen Content in Various Materials (Review)

The review considers published works devoted to the use of the carbothermic reduction method in an inert carrier gas flow for the quantitative determination of the oxygen content in metals and oxides, which is widely applied in metallurgy and semiconductor industry. The scientific foundations of the method, the reduction fusion mechanism, principal features, and the influence of various parameters on analysis accuracy are described. Specimens of diverse materials (oxides as an example) differ substantially in physicochemical properties: melting and boiling points and the thermal decomposition mechanism. Therefore, the methodical approach to the procedure for the determination of the oxygen content in different specimens can differ significantly. Capsules and metallic baths (Sn, Ni, Fe, and Pt) decreasing the reduction temperature and preventing specimen losses are used to enhance accuracy. A specimen weight, a correct blank experiment, and the choice of standards are important factors. A significant attention is given to the hardware: LECO, Horiba, and ELTRA gas analyzers and domestic analogues (METAVAK-K and METEK-600). Modifications of instruments, including the use of boxes with an inert atmosphere for analysis of hygroscopic material, additional filters and traps for volatiles, as well as systems for CO additional oxidation, are considered. These improvements make it possible to diminish inaccuracies, especially for the determination of oxygen at the ppm level.