The thermoluminescent properties of lithium borate activated by silver

To determine the effect of various impurities on the thermoluminescent properties of lithium borate, 60 phosphors were initially prepared which were individually doped with three different concentrations of manganese, cobalt, magnesium silver or one of 15 rare earth elements. Silver and manganese were the only impurities which showed a significant enhancement of thermoluminescence; all others had no effect on lithium borate. The silver activated phosphors exhibited glow curves consisting of peaks at 100° and 175°C, and emission spectra consisting of two broad peaks in the ultraviolet at 290 and 365 nm. The high temperature peak of Li2B4O7: Ag showed good stability at room temperature when stored in the dark; however, considerable fading occurred when the irradiated phosphor was exposed to fluorescent lighting. Lithium borate activated with silver showed a tendency to absorb less moisture from the air than did Li2B4O7: Mn. Because of the high atomic number of silver, the calculated energy response of Li2B4O7: Ag was found to be critically dependent upon the activator concentration at concentrations greater than 0.1 M %. The most favorable theoretical energy response occurs at a concentration of about 0.1 M %. The ultraviolet emission spectrum of Li2B4O7: Ag represents a considerable improvement over the yellow-orange spectrum of Li2B4O7: Mn, with respect to detector efficiency and to infrared blackbody interference. Combined with the proper detection system, Li2B4O7: Ag should be useful for detecting lower radiation exposures than is currently possible with Li Mn, without sacrificing a favorable energy response.