CHARACTERIZATIONS OF OPTICAL-ABSORPTION IN POROUS AL2O3-CR2O3 NANOCOMPOSITES

Optical properties of porous Al2O3 host -Cr2O3 nanocomposites were inv estigated Results show that in each spectrum, four absorption bands (p 1-p4) appear in the wavelength range of 200 to 800nm. P2, p3 and p4 ar e induced by Cr3+ d(3) electronic transitions from the (4)A(2) energy level to the energy level T-4(1), T-4(2), and E-2, respectively The ap pearance of p1 is closely related to Cr3+ and Cr4+. Comparison of abso rption bands for porous nanocomposites with that for single crystal Cr 2O3 indicates ''blue shift'' of absorption bands. With increasing the pyrolysis temperature, p2, p3 and p4 of porous nanocomposites exhibit ''blue shift''. For porous nanocomposites after heating in H-2, p2, p3 and p4 present ''red shift''. The reasons of the absorption band move ment are discussed. (C) 1997 Acta Metallurgica Inc.