ANISOTROPIC OPTICAL-SPECTRA OF YALO3 (YAP) SINGLE-CRYSTALS IN THE VACUUM-ULTRAVIOLET REGION .2. SPECTRA OF REFLECTIVITY

Anisotropic reflectivity spectra of YAlO3 single crystals at 297 K mea sured with the light polarized parallel to each of the a, b and c axes are presented in the range from approximately 6.5 eV to approximately 120 eV. A comparison of the reflectivity spectra of YAlO3 with those of Y2O3, Y3Al5O12 and alpha-Al2O3 single crystals reaffirms that the p eaks at approximately 35 eV are mainly associated with the Y3+4p6 and the features beyond approximately 76 eV with the Al3+L2,3. Anisotropic reflectivity spectra at 10 K are shown in the region from approximate ly 7 eV to 15 eV. Effective optical dielectric constants calculated by the sum rule including the imaginary part of the dielectric constant up to approximately 120 eV are seen to saturate at the values correspo nding to 98.0% approximately 99.7% of the literature values of the opt ical dielectric constant.