Laser-Induced Breakdown Spectroscopy of Molten Metals: Influence of Sample Temperature

The aim of this work was to determine the influence of sample temperature on the laser-induced microplasma (LIP) emission intensity and to ascertain the possibility of laser-induced breakdown spectroscopy (LIBS) utilization for the monitoring of impurities in molten metals. Pure low-melting metals (bismuth, gallium, indium, lead, tin, and zinc) were used for all experiments. It was found out that the LIP emission increases linearly with increasing temperature within the range 25 °C to 70 °C above the melting point of the metal. The slope of this change in LIP intensity is related to the transition probability of a given emission line. If the LIP intensity of given solid and molten metals are compared, then their relative change is related to the coefficient of thermal conductivity. The LIBS shows possibilities for the identification of impurities in molten metals. Amounts of impurities in the order of tens mg/kg can be identified.