ON THE SUBSTITUTION OF FE AND B FOR AL IN THE POLLUCITE (CSALSI2O6) STRUCTURE

The partial or total substitution of Fe and B for Al in the pollucite (CsAlSi2O6) structure was examined or re-examined by means of XRD and FTIR. The samples, prepared through a sol-gel technique, showed a comp lete solid solution series along the join CsAlSi2O6-CsFeSi2O6 and alon g the join CsAlSi2O6-CsBSi2O6, whilst along the join CsFe-Si2O6-CsBSi2 O6 the mutual substitution of boron for iron is no longer complete; in deed a miscibility gap exists, probably due to the large difference be tween the ionic radii of Fe and B. Along the latter join, XRD intensit y measurements on selected samples (CsFeSi2O6, Cs(Fe0.5B0.5)Si2O6 and CsBSi2O6) allowed to carry out their structural analysis in the Space Group Ia3d. (C) 1997 Elsevier Science Limited.