Effects of Postannealing on the Photoluminescence Properties of Coprecipitated Nanocrystalline BaFCl:Sm3+

Nanocrystalline BaFCl:Sm3+, as prepared by coprecipitation from aqueous solutions, is an efficient photoluminescent X-ray storage phosphor. In the present study, we report effects on its photoluminescence properties resulting from postannealing treatment in air in the temperature range between 100 to 900 °C. Interestingly, upon annealing at temperatures from 200 to 600 °C in air, a small fraction of the Sm3+ ions in nanocrystalline BaFCl can be reduced to Sm2+ ions. In addition to the creation of Sm2+ ions, two different sites of Sm3+ ions, denoted as sites A and B, are observed when the nanocrystalline BaFCl:Sm3+ is annealed between 500 to 900 °C. The temperature dependence of photoluminescence properties of the two different sites in the 500 °C annealed sample reveals that the Sm3+ ions at site A are possibly located at or near the crystallite surface, whereas site B is situated in a very ordered environment. To the best of our knowledge, this is the first report on the reduction of Sm3+ ions doped in alkaline-earth fluorohalides to Sm2+ ions by annealing in air

Mechanochemical synthesis of nanocrystalline bafcl:sm storage phosphor by ball milling

The mechanochemical preparation of nanocrystalline BaFCl:Smby ball milling BaClor BaCl2H, BaFand SmFis reported. Photoluminescence shows predominantly SmGHluminescence whereas cathodoluminescence comprises of both the Sm4G6Hand Sm D7Femissions. In comparison with the co-precipitated phosphor, the storage efficiency, as measured by the conversion of Smto Sm upon X-irradiation, is 15 and 6 times lower for the samples prepared by using BaClor BaCl2H, respectively. Importantly, the present result points to the possibility of preparing the entire class of photoluminescent and photostimulable storage phosphors BaFX:RE (X = Cl, Br, I; RE = rare earth element) by ball milling. © 2013 Elsevier B.V

A facile method for the preparation of Eu2+-doped nanocrystallineBaFCl

A facile method for the preparation of Eu2+-doped BaFCl is reported. The method is based on the coprecipitation of aqueous solutions of BaCl2 and NH4F to yield BaFCl. The doping by europium in the 2+ oxidation state is realized by the reduction of Eu3+ to Eu2+ employing granular zinc in the BaCl2 solution under nitrogen. Powder X-ray diffraction and electron microscopy have been used to confirm the BaFCl phase and photoluminescence, in the temperature range of 2.5–290 K, and room-temperature cathodoluminescence spectra have been measured to characterize the Eu2+ ions in the sample