Effect of pressure and temperature on the lifetime of Cr3+ in yttrium aluminum garnet

We have measured the room temperature (RT) and 20 K luminescence lifetime of Cr3+ in yttrium aluminum garnet as a function of pressure up to 240 kbar. The RT lifetime changed from 1.7(1) ms at ambient pressure to 42(2) ms at 220 kbar and the 20 K lifetime from 8.8(1) ms at ambient pressure to 67(2) ms at 240 kbar, the largest value ever observed for a Cr3+-doped material. The distinct pressure dependences of the RT and 20 K lifetimes allowed us to clearly distinguish the contributions of electronic radiative decay, E-2-->(4)A(2) vibronic transitions, and the thermal population of the T-4(2) state to the E-2-->(4)A(2) transition of Cr3+. Analysis of the temperature dependence of the ambient-pressure lifetime showed that both the E-2-->(4)A(2) and T-4(2)-->(4)A(2) vibronic transitions have a significant effect on the E-2-->(4)A(2) luminescence lifetime. Within the context of the single configurational coordinate model, the coupling of the E-2 and T-4(2) states via the spin-orbit coupling (H-SO) and the electron-phonon coupling (H-EP) mechanisms was considered in describing the observed lifetime as a function of pressure. Models formulated in either the H-EP>H-SO or H-SO>H-EP perturbation schemes agreed well with the lifetime data. [S0163-1829(97)02341-2].