The Niobate Complexes

As far as we know the tetrahedral niobate group occurs only in the fergusonite structure of YNbO4 which is a distorted version of the scheelite structure of CaMo04 This luminescence is bright blue and has a relatively high Tq, viz. 500 jfg decay time is 15 MS at 11 which is short in comparison with the plateau value for the molybdate tetrahedron. It is very unfortunate that no more data exist on this complex with its efficient luminescence. 

Upon excitation into the optical band gap an additional emission is observed at longer wavelength. Its origin is thought to be similar to that of the orange emission in CaMo04 (Sect. 3.4.1). 

By studying a large number of compounds containing niobate octahedra it is possible to show the relation between the energy difference between the two parabolae (E p in Fig. 8) and Tq. The reader is referred to previous reviews  

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