Some defects appearing in chromium doped Al 2 O 3 monocrystals as a result of thermal treatment

Results of experiments related to thermal treatment of Al 2 O 3 crystals doped by chromium (ruby) in various gaseous media: CO, H 2 , vacuum and O 2 are given. The kinetics of the formation and destruction of dye centres during this process is discussed. Special attention is given to revealing the causes of the appearance of an absorption band in the region of 315 nm which is related to the internal stability of the crystal with respect to intensive light radiation. – An assumption is made on the nature of the absorption band. – A computation is made of the diffusion coefficient of dye centres related to 315 nm absorption band. This is derived as a function of chromium concentration.