Thermal quenching of F-center luminescence in Al2O3:C

Abstract

Using time-resolved photoluminescence spectroscopy we have measured the lifetime of the F-center luminescence from α-Al2O3:C. The measurements reveal a lifetime of 35–36 ms at room temperature, decreasing to <2 ms over the temperature range from 370 to 500 K. The decrease in the lifetime is shown to follow a classical Mott-Seitz dependence for thermal quenching of luminescence, with an activation energy W of ∼1.08±0.03 eV and a corresponding frequency factor ν of ∼1014 s−1. Similar values for the energy and frequency factor were also obtained from an analysis of thermoluminescence (TL) glow curves measured at different heating rates, when the TL is measured over a wavelength range corresponding to the F-center luminescence emission (centered at 420 nm). Furthermore, the parameters obtained were independent of the glow curve shape, the degree of trap filling, or the specific conditions under which the crystals were grown. This is interpreted as a demonstration that the well-known heating rate dependence of the TL from this material is a result of thermal quenching of the F-center emission. Whereas the thermal quenching parameters obtained from measurement of the luminescence lifetime and from the heating rate analysis of the TL glow curves are independent of the sample type, the degree of trap filling, and the heating or cooling rate, measurements of the photoluminescence intensity, induced by absorption of F-band light, were found to be dependent upon all of the above conditions. This difference in behavior is attributed to a phosphorescence signal from traps associated with the ∼265, ∼310, and ∼450 K TL peaks.

Photoluminescence and Thermoluminescence of the Oxygen-Deficient YAG, YAP, and YAM Phosphors

“…5. As it is seen from the figure, the emission intensity undergoes quenching already at temperatures higher than 80 • C and disappears almost completely at temperatures about 400 • C. This observation is consistent with the quenching of F centers known in Al 2 O 3 :C [3,10]. Typical thermal glow curves of the studied ceramic samples after ionizing irradiation are presented in Fig.…”

Time-resolved optically stimulated luminescence and spectral emission features of α-Al2O3:C

“…[16,17,38] the parameter denotes the background. However, in -Al 2 O 3 :C, B is known to be a temperature-dependent phosphorescence component with a lifetime of several hundred milliseconds [23,25]. This work, for which the dynamic range was only 500 ms, is not concerned with this term.…”

“…Time-resolved optical stimulation should not be confused with time-resolved photoluminescence (TR-PL) where excitation is performed using UV light which directly ionizes F-centres [5,25]. Akselrod et al [25] used this mode to study thermal quenching of luminescence detected at 420 nm.…”

“…Akselrod et al [25] used this mode to study thermal quenching of luminescence detected at 420 nm. Pagonis et al [26] referred to the model of Nikiforov et al [27] and adopted suitable modifications to develop simulations of TR-PL in -Al 2 O 3 :C. In their work, Pagonis et al [26] developed an energy band scheme to explain thermal quenching of the 3.0 eV emission attributed to the 3 P→ 1 S transition at an F centre.…”

“…6,[20][21][22][23][24][25] suggest that although luminescence from -Al 2 O 3 :C has multiple sources [3,28], the contribution from the F-centre is dominant. This is particularly evident when the emission is measured as a thermoluminescence isometric plot above ambient temperature [29,30].…”