Luminescence and excitation spectra of Cr3+:MgAl2O4 nanoceramics

The effect of the applied sintering pressure on luminescence and excitation spectra of Cr3+ doped MgAl2O4 nanoceramics was investigated. It was found that the intensity of E-2 -> (4)A(2) phosphorescence decreased significantly when pumped directly into T-4(1) band. The effect was extremely strong for nanoceramics sintered at higher pressures. Moreover, the intensity of (4)A(2) -> T-4(1) band in excitation spectra drastically decreased with sintering pressure compared to (4)A(2) -> T-4(2) band. This behavior was related to trigonal distortion of Oh symmetry of Cr3+ ion which increases with decreasing the size of nanocrystals resulting in enhancement of the T-4(1) -> T-4(2) nonradiative pathway due to decrease of Delta E (T-4(1), T-4(2)) energy gap. (C) 2013 Elsevier B.V. All rights reserved.