the ultrapure Yb2O3 powders by the CO2-laser radiation with the power PL
100 W at the wavelength 
= 10.6
m at the melting point Tm = 2703 K, forming due to surface tension in melt, and crystallization in air. The analysis of the polycrystal microstructure using the methods of optical and electron microscopy and X-ray dif-
fractometry shows that perfect oxide crystallites are formed in the course of crystallization after melting-
through. The transformation of the luminescence and selective heat radiation (SHR) spectra of the Yb2O3 poly-
crystals is studied under the resonant excitation at
975 nm using a laser diode and the laser heating at the wavelength
= 10.6 m. When the resonant excitation power of the Yb3+ ions increases from 0.15 to 4.5W, the Stokes luminescence of the Yb2O3 polycrystals is sequentially transformed into SHR and the thermal radi-
ation of the crystal lattice. The transformation of the emission spectra of the Yb2O3 polycrystals with an increase
in the laser heating intensity by about four orders of magnitude can be represented as the low-temperature heat
radiation, spectral burst of the thermodynamically nonequilibrium SHR of the Yb3+ ions, and the high-temper-
ature radiation of the crystal lattice. The temperature dependence of the luminescence spectra and SHR of the
Yb2O3 polycrystals on the intensity of the laser and laser-thermal excitation and the concentration quenching
of the Yb3+ luminescence in oxides indicate the key role of the interaction of the f-electron shell of the Yb3+ ions
with the natural oscillations of the crystal lattice in the processes of the multiphonon excitation and nonradiative
(multiphonon) and radiative (vibronic) relaxation.