Neutron scattering study on distribution of cations in α-AgI-type superionic conductors

Neutron diffuse scattering from powder samples of α-AgI type superionic conductors AgI, Ag3SI and Ag2S was measured using a triple-axis spectrometer with a fixed position of the energy analyzer so as to measure only the elastic scattering caused by a disordered distribution of cations. The disorder scattering curves thus obtained were analyzed under the assumption that Ag atoms distribute over crystallographic 12(d) sites among the bcc lattice formed by anions, and probability functions αsub(n) for a simultaneous occupation in the n-th neighbor sites were obtained. The results are discussed comparing with the pair correlation function g sub(Ag-Ag)(r) being obtained theoretically as well as by the analysis of X-ray diffuse scattering based on a liquid-like distribution model. The liquid phase of AgI was also studied by the same neutron technique and the results are discussed together with those for the solid phase. (author)