Abstract
By recent developments in imaging-furnace techniques it is possible to obtain fundamental data on the thermal properties and phase-diagrams of high-melting-point ceramic oxides by a solar furnace. With a heliostat-type solar furnace, temperature and emissivity measurements have been investigated, using a brightness pyrometer designed by our Solar Research Laboratory. Brightness temperature of an opaque body having a specular reflection surface, can be measured by shadowing the marked area of the target surface, rejecting the reflected solar radiation. Spectral reflection is measured after the shadowing mask is removed, and thus the spectral emissivity and true temperature of the specimen can be calculated. In the case of a diffuse-reflection surface, a rotating sector is used to separate the emitted and reflected radiation from the target. The results of freezing-point measurements on HfO 2, ZrO 2, and Al 2O 3 are 3026 ± 20 deg K, 2979 ± 20 deg K, and 2322 ± 15 deg K respectively by the use of specular-reflection method.
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