Thermo-Raman spectroscopic study of the natural layered double hydroxide manasseite

Raman and thermo-Raman spectroscopy have been applied to study the natural hydrotalcite manasseite Mg6Al2(OH)16(CO3)·4H2O. Hydrogen bond distances calculated using a Libowitzky-type empirical function varied between 2.61 and 3.00 Å. Stronger hydrogen bonds were formed by water units as compared to the hydroxyl units. Thermo-Raman spectroscopy enabled the identification of bands attributed to the hydroxyl units. Two Raman bands at 1062 and 1058 cm−1 are assigned to symmetric stretching modes of the carbonate anion. Thermal treatment shifts these bands to higher wavenumbers indicating a change in the carbonate bonding.