Atomic structure of a cesium aluminosilicate geopolymer: A pair distribution function study

The atomic pair distribution function (PDF) method was used to study the structure of cesium aluminosilicate geopolymer (Cs2O center dot Al2O3 center dot 4SiO(2)center dot xH(2)O, with x similar to 11). The geopolymer was prepared by reacting metakaolin with cesium silicate solution followed by curing at 50 degrees C for 24 h in a sealed container. Heating of Cs-geopolymer above 1000 degrees C resulted in formation of crystalline pollucite (CsAlSi2O6). PDF refinement of the pollucite phase formed displayed an excellent fit over the 10-30 angstrom range when compared with a cubic pollucite model. A poorer fit was attained from 1-10 angstrom due to an additional amorphous phase present in the heated geopolymer. On the basis of PDF analysis, unheated Cs-geopolymer displayed structural ordering similar to pollucite up to a length scale of similar to 9 angstrom, despite some differences. Our results suggest that hydrated Cs+ ions were an integral part of the Cs-geopolymer structure and that most of the water present was not associated with Al-OH or Si-OH bonds.