SPECTROSCOPIC AND CRYSTALLOGRAPHIC STUDIES OF YAG-PR4-CRYSTALS( SINGLE)

Y3Al5O12 single crystals doped with praseodymium and magnesium ions ha ve been prepared. The reversible color change of these crystals are ob served when annealing in oxidizing or reducing atmospheres. The change is ascribed to the formation of Pr4+ in the as-grown crystal, caused by the second dopant, Mg2+. The absorption spectra of YAG:Pr,Mg in the range 200-1100 nm, as grown and annealed in air and H-2/N-2 atmospher e, are presented and discussed. Additional broad absorption bands are observed for the as-grown crystals and those annealed in oxidizing atm osphere. Crystallographic investigations of the original crystal and a fter annealing in a reducing atmosphere as described above, show no di stinct structural differences. A redox mechanism is proposed to explai n the color change during annealing. (C) 1998 Elsevier Science S.A.