Physical properties of non-stoichiometric rare earth orthoniobates

Unusual luminescence property of Eu3+ doped non-stoichiometric rare earth orthoniobate, (Gd1-xEux)NbO4-1.5(1-y), prepared using Rb2CO3 flux was studied. The lattice parameters and the photoluminescence intensities vary clearly with the rare earth content of the orthoniobate specimens. The photoluminescence intensity of non-stoichiometric orthoniobate increases as the value of y, decreases, to a maximum at y = 0.6. This enhancement of photolumescence intensity is explained by inefficient non-radiative relaxation of extrinsic niobate center with oxygen deficiency in the non-stoichiometric orthoniobate.