ESCA STUDIES OF FRAMEWORK SILICATES WITH THE SODALITE STRUCTURE .1. COMPARISON OF PURELY SILICEOUS SODALITE AND ALUMINOSILICATE SODALITE

The first detailed X-ray photoelectron spectroscopy (ESCA) study of materials with the sodalite structure shows how the purely siliceous sodalite prepared in a nonaqueous medium differs from the conventional aluminosilicate sodalite and from various zeolites and clay minerals. The purely siliceous sodalite gives a unique set of binding energies and valence band patterns similar to those for silica, while the ESCA pattern of an aluminosilicate sodalite is similar to that of zeolite Na-A. The small differences in binding energies for aluminosilicate sodalite are due to the presence of some K+ and Mg2+ and the fact that the framework Si/Al ratio is slightly higher than unity. While the binding energies for zeolite Na-A and aluminosilicate sodalite form a common set, their ESCA patterns differ substantially from that for the layered aluminosilicate kaolinite. ESCA is thus shown to be sensitive to structure as well as composition.