Unusual cell volume behavior in the LaNbsub(1-x)Vsub(x)O4 system

The crystal structures and lattice constants of the LaNbsub(1-x)Vsub(x)O4 system have been determined at room temperature. The system undergoes a monoclinic to tetragonal phase transformation with an increase in x analagous to the transition as a function of temperature in pure LaNbO4. The unit cell volume increases with an increase in x in the monoclinic phase despite the fact that vanadium is a smaller ion than niobium. A more normal contraction of the cell volume is observed in the tetragonal phase. The origin of this unusual behavior is unclear at present. (Auth.)