The blue thermoluminescence (TL) emission of different thermally annealed (i) β-eucryptite (LiAlSiO4), (ii) virgilite-petalite (LiAlSi5O12) and (iii) virgilite-petalite-bikitaite (LiAlSi10O22) mixed crystals have been studied. The observed changes in the TL glow curves could be linked to simultaneous processes taking place in the lithium aluminosilicate lattice structure (phase transitions, consecutive breaking linking of bonds, alkali self-diffusion, redox reactions, etc). The stability of the TL signal after four months of storage performed at RT under red light, shows big differences between annealed (12 hours at 1200ºC) and non-annealed samples. The fading process in non-annealed samples can be fitted to a first-order decay mathematical expression; however preheated samples could not be reasonably fitted due to the highly dispersion detected. The changes observed in the X-ray diffractograms are in the intensity of the peaks that denote modifications in the degree of crystallinity and, in addition, there are some differences in the appeareance of new peaks that could suppose new phases (e.g. β-spodumene).

Blue thermoluminescence (TL) emission from different lavas of many places (Costa Rica, Canary Islands, Hawaii Islands, Iceland and Italy) corresponding to different eruptions has been studied to know its potential use in the field of dating and retrospective dosimetry. Due to the light emission is linked to the point defects of the crystalline lattice structure, X-ray diffraction analyses were performed to determine the components of this polymineral material that mostly are cristobalite, plagioclase and phyllosilicates. Exposures to different doses (in a range of 1-25 Gy) were given to each sample to determine the evolution of the TL signal with the irradiation under laboratory conditions. In all cases, a linear response could be observed and no saturation has been detected in this range of doses. Both natural (NTL) and induced (ITL) TL signal exhibit a complex glow curve structure associated to a continuous trap distribution over 100°C that could be attributed to the formation-annihilation [AlO4/alcali]+ and [AlO4]° centres. In ITL signal a discrete electron trap distribution (at lower temperature ~85°C) could be detected, thus the coexistence of both trap structure could be appreciated in this material.

En este trabajo se ha estudiado la emisión azul de termoluminiscencia (TL) de lavas de distintas áreas geográficas (Costa Rica, Islas Canarias, Islas Hawai, Islandia e Italia) y procedentes de distintas erupciones, para su posible utilización tanto en el campo de la datación (geológica y arqueológica) como en dosimetría retrospectiva. Debido a que la emisión de luz está íntimamente relacionada con los defectos puntuales existentes en la estructura del material asociados a la presencia de diferentes fases minerales, se realizó un estudio por difracción de rayos X para determinar los principales componentes de las lavas observando la presencia, en distintas proporciones, de cristobalita, plagioclasas y filosilicatos. Cada una de las lavas fueron artificialmente irradiadas para comprobar la dependencia de la señal luminiscente con la dosis en el intervalo de 1-25 Gy, observando una respuesta lineal con la dosis en todos los casos y no apreciándose saturación en la emisión TL. Tanto la señal procedente de muestras naturales (TLN) como las muestras irradiadas en el laboratorio (TLI), mostraban una compleja estructura asociada con una distribución continua de trampas a temperaturas superiores a 100° C, que podría explicarse como consecuencia de la formación-aniquilación dinámica de centros [AlO4/alcali]+ y [AlO4]°. En TLI se observó que a una temperatura próxima a 85°C, aparecía un máximo cuya estructura correspondía a una distribución discreta de trampas, coexistiendo por tanto los dos tipos de estructura de trampas en el mismo material.