Analysis of luminescence spectra of leucite (KAISiO(4))

High-sensitivity radioluminescence (RL) and thermoluminescence (TL) measure ments were carried out on samples of natural leucite (with 2.95% of Na2O) f rom Campania Vessa (Italy). Samples were annealed to modify the charge comp ensation through alkali metal self-diffusion and to produce luminescence ce ntres. High-temperature powder diffraction, scanning electron microscopy an d chemical analyses were performed to monitor the tetragonal-cubic phase tr ansitions and the thermal drainage of alkali metal ions from the aluminosil icate lattice. The emission spectral bands of leucite (300, 380, 430, 480, 560 and 680 nm) match those of other Na/K-aluminosilicates (alkali metal fe ldspars) and could be attributed to similar defects. TL glow curves of incr easingly pre-irradiated natural leucite (range 0-20 Gy) showed no changes a bove 300 degreesC, whereas some changes were observed with annealed samples (1000 degreesC for 12 h). This temperature is the starting point of Na sel f-diffusion within the aluminosilicate lattices. The areas of the TL glow c urves of both natural and annealed beta -irradiated leucites can be fitted with a linear function with high correlation. These results are in agreemen t with high alkali metal loss (K2O similar to 12% and Na2O similar to 18%) during thermal pre-treatment, high cell volume expansion (from 2350 to 2500 Angstrom) and the cubic Ia3d reversible arrow I4(1)/a phase transition. Th is promotes the egress of alkali metal ions and the production of [AlO4/M+] degrees, [AlO4/H+]degrees and [AlO4]degrees luminescence centres.