Effect of preheating in biogenic shells⎯Thermostimulated luminescence and FTIR study

The thermostimulated luminescence (TSL) and Fourier transform infrared (FTIR) measurements were carried out for ten biogenic shells at room temperature (RT) and various temperatures in the range 200-800°C, at an interval of 50°C, for 1 hr duration. The glow curves of unannealed sample show only one peak at 330°C. The sample irradiated with a gamma dose of 500 Gy shows an additional peak at 130°C, when recorded with linear heating rate of 10°C/s. The annealed sample also shows the same trend. Annealing treatment above 250°C increases the sensitivity of 130°C TSL peak. A sudden reduction in TSL sensitivity at 500°C is observed. At this temperature (500°C), FTIR study shows structural disorderedness or phase transition and formation of new structure in the major mineral content. On the other hand, preheating at 700°C caused a collapse in the TSL sensitivity.