Influence of preheating treatment on the luminescence properties of adularia feldspar (KAlSi3O8)

During the firing of ceramics that contain alkali feldspar grains (up to 90 0 degreesC in bricks and 1200 degreesC in porcelains) the metastable equili brium of these natural materials is altered (refractory minerals, neo-forme d minerals and new glassy components). Hence, potassium rich feldspar latti ces, which are being used in some routines of archaeological dating and ret rospective dosimetry, suffer minor modifications by preheating and irradiat ion treatments (K-selfdiffusion, stretching, etc.). In this paper, some pre -heatings of a K-feldspar (adularia) from Saint Gothard (Switzerland) attem pted to simulate the temperatures and conditions undergone in brick manufac turing processes (1000 degreesC for 24 h and 1200 degreesC for 240 h). Some changes in the behavior of the TL and RL spectral curves were detected aft er combinations of thermal pretreatments (at 400 degreesC for 48 h; 500 deg reesC for 72 h; 600 degreesC for 96 h and 700 degreesC for 144 h) and irrad iations. Comparisons between high temperature annealed (1000 and 1200 degre esC) and non-annealed adularias show spectacular changes in the shape of th e TL glow curves: natural-irradiated adularia displays a single large peak at similar to 100 degreesC, whereas annealed adularias show a very complex structure. The observed modifications, probably due to thermal alkali self- diffusion through the lattice interfaces, tilting of the Al-Si crankshafts and phase exsolutions, have been detected by X-ray diffraction. (C) 2000 El sevier Science Ltd. All rights reserved.