Rare earth niobate systems and the phosphor GdNbO4:Bi

An investigation to determine the compounds present in the Ln₂O₃Nb₂O₅ systems (Ln = La, Gd, and Y) and attempts to activate such compounds with Ti, In, Sb, Bi, Eu, and Tb revealed that only the orthoniobate (LnNbO₄) compound was a suitable host lattice and LnNbO₄:Bi under 2537 Å excitation produced the best phosphors. GdNbO₄:Bi is a brighter phosphor than the La and Y analogs, emitting at slightly higher energies. The position of the GdNbO₄:Bi peak emission at 4500 Å is independent of the activator concentration whereas peak emissions for LaNbO₄:Bi and YNbO₄:Bi move to lower energies with increasing Bi concentration.