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Layered double hydroxides (LDHs) containing Mg 2+ , Al 3+ , and Y 3+ in the brucite-like layers and with carbonate as counteranion have been prepared following the coprecipitation method at constant pH. The Al/Y ratio depends on the concentrations in the starting solutions. The crystallinity of the layered materials decreases as the Al/Y ratio increases, probably due to the distortions introduced by the large difference in the ionic radii of the cations. On calcination at 750 °C MgO (probably containing Al 3+ cations) and Y 2 O 3 are formed from the sample richest in Y, while the other samples lead to formation of MgO and presumably Al 2 Y 4 O 9 . At 1000 °C, MgO, MgAl 2 O 4 , and Al 2 Y 4 O 9 are formed in all cases. Exposure of samples calcined at 750 °C in air at room temperature leads to reconstruction of a Mg,Al hydrotalcite and segregation of Y-containing phases.