Evolution of Cr4+, Cr3+ and Cr2+ contents in Cr:Mg2SiO4 single crystals during their prolonged high-temperature oxidizing annealing

Abstract The evolution dynamics of Cr 4+ , Cr 3+ and Cr 2+ contents in chromium doped forsterite (Cr: Mg 2 SiO 4 ) laser crystals during their prolonged high-temperature multi-stage oxidizing annealing have been investigated for the samples grown by Czochralski in ‘standard’ slightly oxidizing atmosphere (Ar +2,2 vol% O 2 ), as well as in inert atmosphere (argon, the residual O 2 content is 0,01 vol%). The contents of Cr 4+ increase by factor of 1,5–3 during the first 800–1000 h of the annealing and then do not change substantially. Cr 2+ practically disappears from the crystals within 800–900 h of the annealing. The content of Cr 3+ passes through a maximum during the annealing. Therefore, this content is determined by two parallel reactions: Cr 2+ →Cr 3+ and Cr 3+ →Cr 4+ .