Thermal radiative properties of ceramic of cubic ZrO2 stabilized with Y2O3at high temperatures

The results are given of the investigation of the normally hemispherical re flectivity of ceramic of cubic zirconia stabilized with 8 mol % yttria for the wavelengths of 0.488, 0.6328, 1.15, and 1.39 mum both in the process of its rapid heating in air by CO2-laser radiation from room temperature to 3 200 K and in the process of subsequent cooling after the heating radiation is discontinued. It is demonstrated that, in the entire investigated spectr al range under conditions of a layer of melt 250-500 mum thick on the surfa ce, an optically infinite layer is realized in the melt, and the reflection is largely defined by the refractive index. This latter layer remains opti cally infinite even immediately after solidification; however, by the end o f the solidification process, its reflectivity somewhat increases due to cr acks and pores. Measurements of the reflection under conditions of continuo us stepwise heating by fluxes of relatively low intensity and in the course of subsequent cooling have produced data on the reflectivity of the layer under close-to-isothermal conditions. Some estimates are made of the values of the absorption coefficient of the melt.