Mechanically activating nucleation and growth of complex perovskites

Mechanical activation of the constituent oxides at room temperature led to the formation of nanocrystalline Pb-based relaxor ferroelectrics and piezoelectrics of complex perovskite structure. The activation-triggered occurrence of complex perovskites, such as Pb(Mg1/3Nb2/3)O-3, 0.9[0.4b(Mg1/3Nb2/3)O-3-0.6Pb(Zn1/3Nb2/3)O-3]-0.1PbTiO(3), and Pb(Zr0.52Ti0.48)O-3, in the mixed oxide compositions and in an amorphous precursor derived from coprecipitation proceeds via a profess involving nucleation and subsequent growth of perovskite crystallites with increasing degree of mechanical activation. This is fundamentally different from the one or more interfacial reactions and diffusions responsible for a thermally activated solid state reaction occurring at an elevated temperature. Nucleation occurs in a highly activated state, where a degree of amorphization has taken place, and the subsequent growth proceeds as a result of the constant collisions and rearrangement of perovskite nuclei. (C) 2000 Academic Press.