Activation of bismuth aluminate for obtaining near infrared emission

New results on NIR emission in Bi2Al4O9 phosphors activated with Cr3+, Er(3+)or Nd3+ are presented. These phosphors were prepared by a simple two step method consisting of combustion followed by annealing at 800C. Annealing step was necessary to obtain powders with good crystallinity; as-combusted powders being amorphous. Host sensitization was observed in all the phosphors. An excitation band around 279 nm corresponds to bandgap excitation of the host S-1(o)-> P-3(1) transition of the Bi3+ ion, while that at 360 nm to the defect absorption. Apart from the excitation in these host related bands, characteristic excitations also produced intense emission lines. It is suggested that these phosphors can be useful for making low cost NIR sources needed in various applications.