Intercalation and Thermal Decomposition of Urea in Layered Zirconium Phosphates of ?- and ?-Type

The intercalation of urea in a- and y- zirconium phosphates was achieved by equilibrating the propanolic form of the two layered hosts with saturated aqueous solutions of urea at room temperature. C, N and H elemental analysis and thermogravimetric determination of a- and y- intercalates, conditioned at room temperature and 75% relative humidity, give the compositions a- Zr(HP04),.0.9 C0(NH2)2.1 .6 H20a nd y-ZrP04(H2P04)1. .2 CO(NH2),.0.6 H20; the interlayer distances of the samples were 1.09 nm and 1.38 nm respectively. FT-IR absorption spectra, analytical data and computer models gave evidence that urea is arranged in the interlayer region as a monolayer. In the 120-220" C temperature range the thermal decomposition of urea in a constrained system gives rise to the formation of the monoammonium form of zirconium phosphates and the elimination of a compound with N/C molar ratio equal to 1.