Blue luminescence in yttrium and gadolinium niobates caused by bismuth. The importance of non-bonding ns(2) valence orbital electrons

A blue luminescent emission band (440 nm) has been optimised in Y1-xBixNbO (x=0.005) for low voltage phosphor applications. The material has useful pr operties when compared to a commercially available phosphor. The role of th e Bi3+ ion dopant is discussed in this lattice and in the related Gd1-xBixN bO4 lattice. The movement of the emission band with %Bi3+ is rationalised u sing a simple electronic band structure model. It is demonstrated that the nature (symmetry) of the chemical environment of the Bi3+ is important for the influence of the cation on the luminescent properties.