Assessment of conversion efficiency of Cr4+ ions by aliovalent cation additives in Cr:YAG ceramic for edge cladding

作者:Chen, Xingtao; Wu, Yiquan*; Lu, Zhongwen; Wei, Nian; Qi, Jianqi; Shi, Yanli; Hua, Tengfei; Zeng, Qiang; Guo, Wang; Lu, Tiecheng*
来源:Journal of the American Ceramic Society, 2018, 101(11): 5098-5109.
DOI:10.1111/jace.15764

摘要

0.25at.% Cr:YAG ceramics were successfully fabricated as the edge cladding of Yb:YAG transparent ceramic slabs through vacuum sintering of co-precipitated powders, using oxide additives to introduce different cations. The effects of various cation additives (Si4+, Ca2+, and Si4+ + Ca2+) on the conversion efficiency of Cr4+ ions and optical characteristics of the Cr:YAG edge cladding were investigated. Measurements of the absorption spectra of the Cr:YAG ceramics without any additives revealed 2 absorption bands centered at 430nm and 600nm, which imparted the sample with a green color. The introduction of only Si4+-bearing additive did not promote the transition of Cr ions from the 3+ to 4+ state. Theoretical analysis and experimentation revealed that the addition of CaO not only enhanced the microstructure and improved the transmittance of the Cr:YAG ceramic, but also introduced vacancies that assisted in the formation of Cr4+ ions. It was determined that CaO has the same effect on the conversion efficiency of Cr4+ ions whether it is added as a single additive or in combination with SiO2. The underlying mechanisms by which these aliovalent cation additives influence the formation of Cr4+ ions and affect optical properties are discussed in detail. High quality composite ceramics with Yb:YAG transparent ceramic slabs and dark brown-colored Cr4+: YAG ceramic edge cladding were achieved through the addition of 0.05 wt.% CaO to the edge cladding, with no interfacial effects between the 2 regions being observed.