Thermoluminescence in Dolomite

The thermoluminescent properties of dolomite have been investigated by coprecipitating impurities which are likely to serve as activators with an otherwise pure sample. Only impurities which are likely to occur in natural samples were considered. The effects of cation and anion vacancies were also investigated and found to be unimportant. Divalent manganese was found to be the only activator of importance and its presence satisfactorily explains the important features of glow curves for natural samples. The results of luminescent efficiency as a function of activator concentration were determined. It was found that concentration quenching of the Mn++ luminescence is characteristic of an isolated activator site. Quenching of the manganese luminescence by Fe++, Co++, and Ni++ was also observed and quantitative results were compiled. All impurity ion concentrations were determined by colorimetric procedures. The presence of Co++ or Ni++ with Mn++ produces high-temperature glow peaks which roughly coincide with similar peaks observed in natural samples. However, it appears more likely that the peaks in natural samples are due to lattice defects resulting from deformation pressures. Isothermal decay curves were measured for all of the glow peaks due to Mn++ and found to have the form predicted for a second-order decay process. However, the behavior of one of the decay parameters as a function of activation time is different from the predicted behavior. The trap depth energies and frequency factors associated with most of the glow peaks due to Mn++ have also been determined.