Melting Point of MgO.

Despite large commercial production of MgO-based ceramics for a wide gamut of applications, the melting point of magnesia remained uncertain for almost one century. This article shows that a number of problems must be solved to attain experimental conditions where the solid–liquid phase transition of magnesia can be unambiguously detected, and the temperature be measured with sufficient accuracy. The method adopted in the reported work is based on controlled laser pulse heating. The solidification point was measured by the thermal arrest occurring during cooldown from the melt. The measurement of temperature, a most delicate problem for pyrometry applications in semitransparent materials, was obtained by using combined brightness and spectral pyrometers. The experimental and analytical methods are described in some detail. The resulting melting point of MgO is 3250±20 K, which is approximately 150 K higher than the value currently recommended.