Synthesis, Structure, and Heat Capacity of Some Basic Hydroxohalide Glasses of Zirconium and Hafnium

This work highlights the synthesis and properties of novel basic hydroxohalide glasses of zirconium and hafnium. The hydroxohalide glasses are M(OH)_4-αX_α·(n)H₂O where M represents either zirconium or hafnium, and X represents either chloride or bromide. The chemical structure is investigated using X-ray diffraction, total scattering, and the pair distribution function method to identify the local structure and any short-range connectivity. The thermodynamic properties of the glasses are probed using low-temperature heat capacity, where a gap in the phonon density of states is discussed and related to boson peaks in the heat capacity of the glasses. These results represent the first published synthesis and thermodynamic properties of zirconium and hafnium basic hydroxohalide glasses. Synthesis methods, structural determination, and analysis of the heat capacity data allow for a comprehensive look at the makeup and unique properties of these novel glassy materials. Values of the standard thermodynamic functions C_p°, Δ₀S_m°, Δ₀H_m°, and Φ_m° are also reported.