Etude de la diffusion des cations Cu⁺ dans le verre (CuPO₃)_0.5(CuI)_0.5 par diffusion quasielastique des neutrons

A neutron scattering experiment was performed on the fast ionic conductor (CuPO₃)_0.5(CuI)_0.5 using the time-of-flight spectrometer IN6 with the following parameters: λ = 5,1 A ̊, resolution (FWHM) E_o = 80 μev, 1.44 < Q < 2.04 A ̊^-1. The spectra essentially consist of a quasielastic broadening of the elastic peak with a long inelastic tail up to 20 meV. The deconvolution of elastic and quasielastic contribution gives a constant value of the purely elastic contribution : 90 % for three temperatures. The D coefficients obey an Arrhenius law : D=2.57×10^-5exp( -Ea RT)cm²s^-1. with E_a = 2.6 KJ.mol^-1. Only 22 % of Cu⁺ ions are implied in the diffusion motions compared to 50 % of Ag⁺ ions in the superionic AgPO₃-AgI glass. The activation energy is much lower than the results previously obtained on Ag⁺ glasses. The motion described here certainly occurs locally without leading to long range diffusion which is involved in ionic conductivity.