New explanation for oxidation-induced Cr4+ formation in garnets

Abstract

The demand for self-Q-switched lasers caused a growing interest in Cr4+:YAG materials. However, the main problem of Cr4+:YAG is an insufficient concentration of Cr4+ ions. This problem is complicated by the absence of the adequate model describing formation of Cr4+ ions. Analysis of the temperature dependence of Cr3+ luminescence in the Cr-doped YAG ceramics after different thermal treatments allows understanding the mechanism of Cr3+-Cr4+ valence transformation. Two types of Cr3+ centers with different spectroscopic properties were revealed in the Cr,Ca-doped YAG ceramics, namely, single Cr3+ ions, and Cr3+/ [CaC′…VO·] couples. Using the obtained spectroscopic data, a model of formation of Cr4+ ions in YAG lattice was proposed.

Keywords

• Transparent ceramics
• Temperature dependence
• Luminescence
• Charge compensation
• Transition metal