Formation of color centers in yttrium orthoaluminate crystals

An analysis is made of the absorption spectra of color centers formed in YAlO₃ and YAlO₃:Nd crystals under the action of a xenon flashlamp, gamma radiation, and heat treatment in different atmospheres. It is found that the nature of the color centers is governed by the growth conditions and does not depend on the neodymium ions. Yttrium orthoaluminate crystals grown in a vacuum undergo negligible coloration whereas those grown in argon exhibit the same color centers after exposure to gamma and ultraviolet radiation and after oxidizing heat treatment. The optical stability of these color centers and the relationship between the concentrations of centers with different structures both depend on the type of exposure.