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Thermal radiation and optical properties of cubic zirconia stabilised with yttria up to the temperature of high rate evaporation
Vadim Petrov, Aleksey Vorobyev, Aleksander Chernyshev

The normal-hemispherical reflectivity at the wavelengths of 0.488, 0.6328, 1.15, and 3.39 μm of cubic zirconia ceramics stabilised with 8 mol% yttria was measured in the course of rapid heating in air by concentrated CO2 laser radiation from room temperature to 3200 K and in the process of subsequent rapid cooling when the heating radiation was switched off. The results are presented and analysed. It is shown that, in the entire studied spectral range, with a molten layer 250 – 500 μm thick on the surface, an optically infinite layer is realised in the melt, and the reflection is mainly defined by the refractive index. This layer remains optically infinite just after solidification; however, by the end of the solidification process its reflectivity increases slightly owing to cracks and pores. Measurement of the reflection under prolonged stepwise heating by laser radiation fluxes of relatively low intensity and in the course of subsequent cooling provides data on spectral reflectivity under conditions close to isothermal. Some estimates for the absorption coefficient of the melt are given.

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