1 THE DISTRIBUTION OF Ga IN Ga-PILLARED MONTMORILLONITES: A TRANSMISSION ELECTRON MICROSCOPY AND MICROANALYSIS STUDY

The distribution of Ga in the interlayer of montmorillonite pillared with a Ga13 polyoxocation complex has been studied by transmission electron microscopy, energy-dispersive X-ray microanalysis (EDX), X-ray mapping and powder X-ray diffraction in combination with N2 adsorption-desorption. To view the clay layers by TEM, the pillared clay was embedded in Spurrs resin in a preferred orientation, and sectioned with an ultramicrotome perpendicular to the layers. Montmorillonites pillared with Al13 and Al12Ga complexes were also prepared for microanalysis in the TEM. The Ga X-ray peaks could be easily distinguished in the EDX spectra, allowing concentrations relative to other elements to be determined. Elemental X-ray maps for Ga, Si and Al in the Ga13 pillared clay cross-sections demonstrated that the Ga was homogeneously distributed throughout the crystal thickness. Comparison of the analytical data with that from the Al13 and Al12Ga pillared clays and the starting material suggested that an approximately constant amount of the intercalated species per amount of Si in the clay became incorporated into the structure in each case. Calculation of the formula for the Ga-pillare