It was suggested that the monitoring of infra-red luminescence along the diffusion direction of activator ions in these crystals was a sensitive and minimally invasive method for determining diffusion coefficients, diffusion enthalpies and the temperature dependences of these parameters. The technique was used to study the diffusion of Nd3+ in AgBr crystals. The results (figure 1) could be described by:

D (cm2/s) = 1.2 x 10-5 exp[-0.51(eV)/kT]

It was found that high values of the diffusion coefficient, and low values of the diffusion enthalpy, facilitated the preparation of high optical quality Nd-doped AgBr crystals.

Luminescence Method for the Study of Nd3+ Ions Diffusion in AgBr Crystals. L.Nagli, A.German, A.Katzir: Journal of Applied Physics, 1999, 85[4], 2114-8