Thermoluminescence and cathodoluminescence studies of calcite and MgO: Surface defects and heat treatment

Geologically-formed calcite is a suitable material for dating, using thermoluminescence (TL) and electron-spin-resonance. However, many problems preclude accurate age determination. Some of these problems stem from different sample pre-treatment procedures, such as grinding, drilling or pre-heating. It has long been known that grinding can introduce spurious TL in calcite, but there have been wide differences of opinion as to the magnitude of the influence and its importance. Therefore, various grinding and acid-washing procedures have been suggested to avoid spurious thermoluminescence. Various models have been developed to explain the mechanism. We have studied the changes in thermoluminescence (TL) and cathodoluminescence (CL) properties as well as in the spectral composition of the glow from calcite and MgO due to surface defects and heat treatment. It is found that both laboratory heat treatment and surface indents give rise to changes in TL efficiency.