Comparisons of thermoluminescence signals between crystal and powder samples

Abstract

Thermoluminescence data for several materials show that there are measurable differences between signals from crystalline and powder variants. With examples starting with crystalline calcite, Iceland Spar, and aragonite, and calcium fluoride (with rare earth impurities) the crushed material has altered signals. The changes are variously (i) alterations in the relative intensities of the glow peaks, (ii) modifications of the emission spectra, (iii) higher intensity per unit weight from the powdered material and (iv) examples with different numbers of peaks. (v) Whilst the thermoluminescence peaks sometimes appear at lower temperatures, which is consistent with features (i) to (iv), caution is required as there can be experimental reasons which also result in lowered temperatures. These include altered thermal coupling and/or temperature gradients at the sample heater. The scale of potential experimental variations is surprisingly large, and they have relevance to all thermoluminescence studies. Examples of such effects have been noted and new suggestions to minimise them are presented.