Blue luminescence in yttrium and gadolinium niobates caused by bismuth. The importance of non-bonding ns2 valence orbital electrons

Abstract

A blue luminescent emission band (440 nm) has been optimised in Y_{1 – x}Bi_xNbO (x = 0.005) for low voltage phosphor applications. The material has useful properties when compared to a commercially available phosphor. The role of the Bi³⁺ ion dopant is discussed in this lattice and in the related Gd_{1 – x}Bi_xNbO₄ lattice. The movement of the emission band with %Bi³⁺ is rationalised using 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.