MVO4-Ta2O5-Nb2O5 (M = Y, La) solid solutions

The subsolidus phase relations in the MVO4-Ta2O5-Nb2O5 (M = Y, La) systems were studied. MNb2-2xTa2xVO9 (I) and MTa2-2xNb2xVO9 (II) solid solutions we re prepared and characterized by x-ray diffraction, vibrational spectroscop y, and electron spin resonance. The range of solid solutions in I is x = 0- 0.58 for M = Y and 0-0.4 for M = La; in II, x = 0-0.09 for M = Y and 0-0.1 for M = La. All of the solid solutions were found to contain V(IV) centers whose nearest neighbor environment depended on composition. The structure o f LaTa2-2xNb2xVO9 was shown to contain fragments characteristic of LaNb2VO9 . The lattice parameters of these solid solutions correlate with the V(IV) content.