Structure and transmittance of Cr3+ doped MgO·nAl2O3 (0.9≤n≤1.2) ceramics

Transparent spinel ceramics (MgO·nAl 2 O 3 , n = 0.9–1.2) doped with Cr 3+ ions were prepared by hot-pressed sintering in a vacuum. The effect of the composition on the microstructure, densification , and transmittance of ceramics was studied. The single phase of spinel was obtained at n ≥ 0.95, and their relative density changed insignificantly and was about 99%. As the n value increased, the Al 3+ ions were preferred to locate the tetrahedral sites in the spinel structure. At n = 1, approximately 65% of Al 3+ ions occupied the T-sites, and at n = 1.2, it increased to 77%. The occupation of Cr 3+ ions was not affected by the Al 3+ occupation, and the ratio of Cr 3+ ions in T-sites to O-sites was still about 1:1, regardless of the value of n. The transmittance of the ceramics was relatively high at 1≤n ≤ 1.1, and the transmittance in the region of 1000–6000 nm was about 74–78%.