A 1H NMR relaxation time study of dynamic processes in zirconium phosphates of differing crystallinities and in related compounds

Abstract

The temperature dependences of the 1H NMR relaxation times T 1, T 1ϱ and T 2 are reported for crystalline zirconium phospha te and for related compounds which also have the α-layered structure: zirconium phosphate (ZrP, Zr(HPO 4) 2·H 2O), zirconium phosphate phosphite (ZrPP, Zr(HPO 3) 1,2(HPO 4) 0.8·0.5H 2O), pellicular zirconium phosphate (p-ZrP, Zr(HPO 4) 2·1.2H 2O) and its ammonitated daughter compound ((NH 4) 1.8H 0.2[Zr(PO 4) 2]·0.8H 2O). Variations in the forms of the temperature dependences are directly linked with variations in structure. In the ordered crystalline materials single minima in spin-lattice relaxation time ( T 1) are assigned as arising from 180°-flips of interlamellar water molecules; in p-ZrP the disordered interlayer region results in a distribution of reorientational correlation times. Two minima in T 1 are observed for each of p-ZrP and its ammoniated daughter compound; the higher temperature minimum arises from interlamellar species (H 2O in p-ZrP and NH + 4 in the ammonium compound) and the lower temperature minimum is assigned to those same species present in defects and having a consequent distribution of correlation times.