THERMAL BEHAVIOR OF PHOSPHATE INTERCALATED Mg/Al-LAYERED DOUBLE HYDROXIDES

The thermal behavior of Mg and Al layered double hydroxide with interlayer hydrogen phosphate (abb. as Mg/Al-HPO₄-LDH) is investigated below 1273 K by means of XRD, TG-DTA, SEM and FT-IR. The basal spacing of Mg/Al-HPO4-LDH decreases with increasing heating temperature stepwise in two stages; from 1.07 nm at 293 K to 0.85 nm at 333 K in the first stage and to 0.73 nm between 373 K and 443 K in the second one. The LDH becomes amorphous above 443 K until Mg₃ (PO₄)₂, MgO and MgAl₂O₄ (spinel) appear at 1273 K. SEM images of the LDH show plate-like crystallites both before and after heating at 473 K.