Diffusion of Pr3+ ions in silver halide crystals

The diffusion of Pr3+ ions in AgBr and AgCl0.77Br0.23 single crystals has b een investigated by a method based on measuring the luminescence intensity distribution along the diffusion direction. The diffusion constants D-0 for these crystals were 3.8 x 10(-6) and 7.95 cm(2)/s; and the enthalpy of dif fusion H values were 0.4 and 1.25 eV, respectively. A strong influence of t he silver halide composition on Pr3+-ions diffusion parameters was observed . The low value of the diffusion enthalpy found for these ions is described in terms of an associated complex 3(+)-ion - cation vacancy motion by an e xchange mechanism. The influence of the radius of the rare earth ions on th e diffusion enthalpy is discussed. (C) 2001 Elsevier Science B.V. All right s reserved.