Infrared,Raman and neutron scattering studies of β- and β″-alumina: a static and dynamical structure analysis

Infrared and Raman data on β-aluminates with different compositions (x)=0.0, 0.25, 0.66) containing Na⁺, Ag⁺, K⁺, Tl⁺, H₃O⁺, NH⁺₄ ions are reviewed. β-gallates and β″-aluminates are also considered. Assignments of the cation modes are discussed in terms of oscillations of single cations and of normal modes of clusters (pairs and triangles formed by the conducting cations). The assignment of the spinel block spectra is proposed in the light of recent normal mode calculation and comparison of different experimental results in the literature. Potential barriers and activation energies obtained from these techniques are compared with calculation results and with data obtained from different sources. Inelastic and recent quasi elastic neutron scattering results are reviewed and compared with those deduced from the vibrational study.