Mass Spectrometric Determination of Activity of Phosphorus in Liquid Fe-P Alloy

Abstract

The activities of P and Fe in a dilute solution of P in liquid iron at 1600°C have been determined with a combination of a mass spectrometer and a Knudsen cell; a magnetic deflection type mass spectrometer was used. A pulse counting system was used for the measurement of the ion currents of P⁺ and P⁺₂, for the intensities of these ions were very small; the relatively large ion currents of Fe were measured with a DC amplifying system. The whole system was computer-controlled, and a high sensitivity with a large dynamic range and considerable resolution could be obtained by using this system.
The range of the concentration of phosphorus was from 0.7wt% to 3.2wt% (1.3at% to 5.7at%), and the method based on the G_IBBS-D_UHEM relation was used to obtain the interaction coefficient, ε^P_Pfrom the obtained ion current ratios, and ε^P_P= 7.3±0.1was obtained.
The accuracy and the precision of the obtained value are discussed.