In accordance with the existing tendency toward acceleration of the process occurring in combustion chambers, there has been an increase in interest in the use of heat-protective and thermal-insulation materials with higher operating characteristics, particularly increased refractoriness.Wide use of zirconium dioxide has started. However, the radiation characteristics of ZrO 2 have been insufficiently investigated.Existing works [1][2][3][4][5] have been done in a relatively narrow range of influencing conditions of wavelengths, temepratures, etc. The spectral degree of blackness was investigated.Investigation of the reflective characteristics provides more information on the radiation properties of a body than the emissive. First, in investigation of the bidirectional reflective characteristics it is possible to obtain the angular distributions of the reflected radiation with a change in the angle of incidence.And, second, with appropriate information it is quite simple to convert from the reflective radiation characteristics to the emissive characteristics [6]. The reverse operation is difficult and therefore we investigated the characteristics of the zirconia refractory in the wavelength range from 0.75 to i0 um. The experimental unit, the method of the investigations, and the data processing were described in detail in [7]. Magnesium oxide and sodium chloride were used as the standards in investigation of radiant properties of zirconium dioxide.The first was used in the 0.75-2.5 ~m wavelength range and the second in the 2.50-I0-~m range.The refractory specimens were disks with a diameter of 20 and a thickness of 10-15 mm. The experiments were made for two types of zirconium dioxide refractory, dense with an open porosity of 0.5% and porous with an open porosity of 20%.The refractories differed primarily in grain size. The dense specimens had a grain size of 0.002 mm and the porous of 0.5 mm. In both cases CaO was used as the stabilizer.

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