Cluster linkages between luminescence emission spectra and continuous trapdistribution in a volcanic sanidine

Abstract

Volcanic sanidine shows two important characteristics involved in the luminescence emission: (i) a near-infrared emission centred around 700 nm, attributed to Fe3+ substituted for Al3+, and (ii) a Si¿Al highly disordered crystallographic lattice of natural, recently pre-annealed feldspars. Thermoluminescence emission spectra have been obtained from well-characterised transparent crystals of sanidine using a high sensitivity spectrometer. Tests of thermal stability at di9erent temperatures show a continuous trap distribution with progressive changes in the glow curve shape, intensity and temperature position of the peak maximum. The characteristic broad blue emission band displays cluster linkages between blue and red emissions which can be explained by thermal alkali self-di9usion through both bulk and interfaces producing redox changes of the iron ion valence. These complex phenomena could also explain the large fading and tunnelling recombination of sanidine.