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Mixed-order kinetic analysis of the glow curve characteristics of single crystal LiF:Mg,Ti as a function of Ti concentration

1998; Elsevier BV; Volume: 29; Issue: 5 Linguagem: Inglês

10.1016/s1350-4487(98)00050-x

1879-0925

Yoav Weizman, Y.S. Horowitz, L. Oster, D. Yossian, O. Bar-Lavy, A. Horowitz,

Advanced Chemical Physics Studies

The glow curve characteristics of single crystal LiF:Mg,Ti, grown by the Bridgman method, were studied as a function of Ti concentration (3–14 ppm Ti). The glow curves were deconvoluted into component glow peaks using mixed-order (MO) model kinetics. The thermoluminescence (TL) sensitivities of all the low temperature peaks (peaks 2–5) increase with increasing Ti concentration, reaching a maximum at 12–13 ppm Ti. The increase of peak 5 sensitivity is especially dramatic, a factor 10 higher at concentrations above 10 ppm compared to the lower sensitivity over the range of Ti concentrations from 3–6 ppm. In glow curves without a post-irradiation anneal, the activation energies of peaks 2 and 3 are constant as a function of Ti concentration, 1.3±0.1 and 1.15±0.1 eV respectively. The activation energy of peak 4, however, increases, with a correlated decrease in the activation energy of peak 5. In glow curves following a 165°C/15 min anneal to remove peaks 2–4, the activation energy of peak 5 was observed to increase from 1.65±0.1 eV at the lowest Ti concentrations to 1.9±0.1 eV from 8–14 ppm Ti concentration. The unique behaviour of peak 5 is interpreted as additional evidence indicating that peak 5 arises from a complex TC/LC spatially correlated defect structure, Mg trimers coupled to Ti, and that the Ti ions perturb the TC, thereby leading to a change in the activation energy.