ULTRAMARINE, LAZURITE AND SODALITE STUDIED BY POSITRON-ANNIHILATION AND EPR METHODS

Studies of positron annihilation accompanied by EPR technique were und ertaken for sodalite and lazurite and their synthetic counterparts (sy nthetic sodalite and ultramarines). Results of measurements performed by two techniques of positron annihilation spectroscopy (angular corre lation of annihilation radiation, ACAR, and positron annihilation life time) revealed the undoubted influence of free radicals on positron an nihilation mechanism but both inhibition of positronium formation by t hem and the effect of filling cages ought to be taken into account. Th e distinct differences between ACAR curves for sodalites, lazurites an d ultramarines probably reflect the presence of different radicals in their cages and chemical heterogeneity as well as the disorder in Al, Si-site ordering in case of ultramarines. Comparison of the results of ACAR measurements with the ones of the EPR studies indicates that the re is correspondence between them. Similarly to three families of the ACAR curves, different types of EPR lines were obtained for three grou ps of samples; sodalites, lazurites and ultramarines. It is possible t hat the annihilation of positrons takes place mainly with unpaired ele ctrons recorded by the EPR technique.