Synthesis and Raman spectroscopic characterisation of hydrotalcites based on the formula Ca6Al2(CO3)(OH)16· 4H2O

Abstract We have successfully synthesised hydrotalcites (HTs) containing calcium, which are naturally occurring minerals. Insight into the unique structure of HTs has been obtained using a combination of X‐ray diffraction (XRD) as well as infrared and Raman spectroscopies. Calcium‐containing hydrotalcites (Ca‐HTs) of the formula Ca4Al2(CO3)(OH)12·4H2O (2:1 Ca‐HT) to Ca8Al2(CO3)(OH)20· 4H2O (4:1 Ca‐HT) have been successfully synthesised and characterised by XRD and Raman spectroscopy. XRD has shown that 3:1 calcium HTs have the largest interlayer distance. Raman spectroscopy complemented with selected infrared data has been used to characterise the synthesised Ca‐HTs. The Raman bands observed at around 1086 and 1077 cm−1 were attributed to the ν1 symmetric stretching modes of the (CO32−) units of calcite and carbonate intercalated into the HT interlayer. The corresponding ν3 CO32− antisymmetric stretching modes are found at around 1410 and 1475 cm−1. Copyright © 2010 John Wiley & Sons, Ltd.