From incipient ferroelectricity of nano-confined water molecules in beryl to their relaxor-like behavior in cordierite

Abstract: Earlier [10.1038/ncomms12842 (2016)], we have observed incipient ferroelectric behavior among water molecules localized within nano-size cages formed by ions of crystal lattice of beryl. Emergence of macroscopic polarization among H2O molecular dipoles is suppressed due to quantum tunneling within hexagonal potential. Like in beryl, in cordierite water molecules are located within nano-cages and can relatively freely rotate around the c-axis experiencing 2-well potential with the depth of ~10 meV. Dielectric spectroscopy reveals typical (anisotropic within ab plane) relaxor-like response of confined water molecules connected with a broad soft relaxation with complicated lineshape. At terahertz frequencies, sharply anisotropic soft-mode response is observed caused by dynamics of water molecular ensemble. We shall present temperature-dependent RF-THz-IR spectra of water-containing cordierite crystal and suggest possible interpretations of the observed phenomena.