Synthesis and structure of lithium cesium and lithium thallium cancrinites

Abstract

Listen

Translate article

X-ray powder diffraction studies of synthetic cancrinites were undertaken to elucidate the role of lithium ions and large cations (Cs, Tl) in zeolite crystallizations. Li4.56Cs1.50Al6Si6O24, 4.9 H2O (a = b = 12.4328 (12) Å, c = 4.9692 (6) Å, hexagonal, P63, Z = 1). The structure was refined by the Rietveld diffraction-profile refinement technique. The cesium ions — located in the cancrinite cage only — are coordinated to 12 oxygen atoms (at distances 3.15–3.61 Å). In accordance with their position, they are not exchangeable. The lithium ions are four coordinated to oxygen atoms (at distances 1.91 to 2.03 Å). Li2.75Tl3.23Al5.85Si6.13O24, 2.0 H2O (a = b = 12.4419 (7) Å, c = 4.9884 (4) Å, hexagonal, P63, Z = 1. The thallium ions are located on more than one position in the cancrinite cage, and there is also thallium on one position in the channels. This is in accordance with the thallium ions being partially exchangeable in this material. The structures are described and the action of small and large ion radius cations in cancrinite crystallization is discussed.