LUMINESCENCE IN NATURAL APATITE AND APATITE PHOSPHORS

Natural apatite frequently displays strong luminescence under cathode ray stimulation (Cathodoluminescence) and under ultraviolet excitation (Photoluminescence). The luminescence is due in part to the insulating properties of the apatite and the large band gap, and to the favorable structure which can accommodate rare earths, transition metals, polyanions, and closed shell metal activators and sensitizers. Besides the beauty of the luminescence itself, which can take on practically any color, the emission spectrum can be used as a sensitive tool for trace ion detection and characterization, for analysis of growth history (via analysis of sector and concentric zoning), and for analysis of thermal and chemical variations both during and post growth. Synthetic halide apatites are also important phosphors, notably in fluorescent and projection lamps, and apatite-structure crystals are actively studied as laser hosts. This review will show examples of natural apatite luminescence, and describe briefly some of the connections between luminescence features and various aspects of trace metal chemistry and apatite formation conditions. Opportunities for future research involving both classical and new technologies will also be discussed.