Luminescence of natural sapphire (alpha-Al2O3) and diaspore (alpha-AlOOH) associations

Abstract

Natural mixtures of sapphire (#1;-Al2O3) and diaspore (#1;-AlOOH) samples from Goian (NW Spain) have been analysed by scanning electron microscopy, electron microprobe, spectral luminescent techniques (thermoluminescence, radioluminescence, cathodoluminescence) and inductively coupled atomic plasma bulk analyses. Blue coloured areas could be attributed to chromophore elements (FeO=0:278%, TiO2 =0:023%) and the large photon emission peak observed at 700 nm with 80 ppm of Cr2O3. Additional smaller bands at 670 and 720 nm can be assigned to Ti4+ and FeO in the lattice. The coexistence of two different types of luminescent behaviour in the lattice of this material, such as a discrete electron trap distribution at lower temperature (circa 190ºC) and a continuous trap structure at higher temperature (over 250ºC) and their relationship with dehydroxylation and chromophore oxidation are explored