Thermo‐Raman spectroscopy of selected layered double hydroxides of formula Cu₆Al₂(OH)₁₆CO₃ and Zn₆Al₂(OH)₁₆CO₃

Raman spectroscopy using a hot stage was used to characterise layered double hydroxides (LDHs) of the formula (Cu,Zn) 6 Al 2 (OH) 16 (CO 3 ) · 4H 2 O. The spectra were used to assess the molecular assembly of the cations in the LDH structure. The sharp band at 1058 cm −1 for the Zn 6 Al 2 (OH) 16 (CO 3 ) · 4H 2 O is assigned to the ν 1 CO 3 2− symmetric stretching mode. This band shifts to higher wavenumbers and is observed at 1103 cm −1 at 600 °C. It is proposed that metal carbonate species formed during the decomposition of the hydrotalcite structure is responsible for the increase in the band position. The Cu–Al hydrotalcite did not show the same trend. The symmetric stretching mode of carbonate is observed at around 1110 cm −1 , and at temperatures above 200 °C a shoulder appears at around 1210 cm −1 , suggested to be due to CuCO 3 .