Microstructure, properties and thermoluminescent response of sintered synthetic topaz (Al₂SiO₄F_1.44 (OH)_0.56)/Al₂O₃ compounds

Because of variations in composition and the ensuing properties of mineral topaz, synthetic topaz offers to be a promising candidate for advanced applications. The thermoluminescent response of sintered synthetic Al₂SiO₄F_1.44(OH)_0.56 (topaz)/Al₂O₃ (corundum) compounds, was studied for the first time. From an L8 Taguchi experimental design, topaz specimens synthesized by CVD were thermally treated varying temperature (850, 1000 °C), time (30, 60 min), powder compaction pressure (250, 500 MPa), atmosphere (N₂, Ar) and tablet position in the reactor (0, 90°). XRD analysis confirms the presence of Al₂SiO₄F_1.44(OH)_0.56 as a single phase in the as-processed condition and of Al₂O₃ besides topaz, in the sintered state. Specimens sintered at 850 °C feature prismatic bars with pyramidal ends, of uniform distribution and average length between 5.03–6.02 μm. A series of possible chemical reactions giving place to the topaz formation and subsequent sintering-associated reactions is put forward. Associated with [AlO₄]° centers, the presence of two well resolved and independent peaks between 150−250 °C in the TL glow curves and the linear response in all tested samples as dose increases (0.02 Gy–66 Gy), encourage further research to increase dose range linearity and paves the way for possible application of the sintered synthetic topaz/corundum compounds in dosimetry.