Novel luminescence of pristine BaFBr prepared by non-equilibrium laser-heating technique

Results of room temperature photoluminescence studies carried out on undoped (pristine) single-phase BaFBr compound, prepared in air by laser heating are presented. On irradiation using 266 nm, we find an intense and broad emission band peaking at 466 nm and another relatively narrow band at 313 nm. The former band is indicative of presence of stable OF2− centres while the latter is a signature of stable VK(Br2−) centres in the matrix. The unusual and new observation of strong luminescence from both types of centres at room temperature has been interpreted as possibly be due to their stabilization by various defect entities in the BaFBr matrix formed on account of the non-equilibrium manner in which the sample has been prepared by the novel laser-heating technique. An interesting oscillatory temporal behaviour of the 466 nm peak intensity upon constant UV irradiation at 266 nm is also reported.