Synthesis, Structural Characterization, and Thermal Stability of a New Layered Germanate Structure, Na₄Ge₁₆O₂₈(OH)₁₂

The new layered germanate structure Na4Ge16O28(OH)12 has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, FTIR, and SEM. The crystal lattice parameters are a = 7.3216(6) Å, b = 14.3986(9) Å, c = 7.7437(6) Å, α = 90.0°, β = 100.179(7)°, γ = 90.0°, and V = 803.5(1) Å3. The space group is C2/m with Z = 1. The germanium oxide sheets are connected non-covalently via electrostatic interactions with the sodium cations and H-bridging. At temperatures above 400 °C, the structure starts decomposing into sodium enneagermanate (Na4Ge9O20), germanium dioxide, and water as determined by powder X-ray diffraction, TGA, DTA, DSC, and GCMS.