Radiation defects in feldspars

Various radiation defects were characterized and analyzed by electron paramagnetic resonance (EPR) in 15 feldspars of different compositions after X-ray irradiation. A hole center on oxygen adjacent to two aluminum ions is formed in most feldspars, except those with very high An content. Since the hole is not localized at room temperature, clusters of more than two Al must be present in all feldspars in amounts of at least 100 ppm. Less frequent radiation defects are trivalent titanium and holes on oxygen ions adjacent to a small divalent ion of a yet unidentified nature on a T site with Si and in some cases also Pb as further neighbors. The directions of the magnetic axes for these centers allowed their assignment to specific sites in the feldspar structure. Characteristic absorption and thermolu-minescence emission bands could also be assigned to these centers. Their properties are remarkably independent of composition and Al, Si disorder of the feldspars.