Divalent and trivalent neodymium photoluminescence in NaMgF3:Nd

Photoluminescence from Nd3+ and Nd2+ ions was observed in polycrystalline NaMgF3:Nd synthesised via a high-temperature melt, slow-cooling technique. The spectral features of Nd3+ were directly attributed to known intraconfigurational 4f3 → 4f3 transitions, where numerous emissions occurred in the infrared spectral region 840 nm–1390 nm. Additional emissions were observed over the range 850 nm–1500 nm that could not be attributed to Nd3+. The additional emissions were attributed to specific intraconfigurational 4f4 transitions of Nd2+ via comparison of the photoluminescence features with the known transitions of the isoelectronic Pm3+ ion in similar host compounds. The energies of the Nd2+ 4f4 levels were compressed by a factor of 1.09 relative to the Pm3+ ion. X-ray irradiation produced a radiophotoluminescence effect whereby the Nd2+ emission intensities increased for optical stimulations below 450 nm. Continuous stimulation at 400 nm reversed this effect. This phenomenon could be useful for applications in infrared lasing, radiation detection, and optical information storage.