The role of crystallite size and clustering in influencing the stability of the structures of a large tetragonality ferroelectric system 0.6BiFeO 3 –0.4PbTiO 3 was investigated. The system exhibits cubic phase for a crystallite size ∼25nm, three times larger than the critical size reported for one of its end member PbTiO 3 . With increased degree of clustering for the same average crystallite size, partial stabilization of the ferroelectric tetragonal phase takes place. The results suggest that clustering helps in reducing the depolarization energy without the need for increasing the crystallite size of free particles.