Mechanically activating nucleation and growth of complex perovskites

Abstract

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(Mg(1/3)Nb(2/3))O3, 0.9[0.4Pb(Mg(1/3)Nb(2/3))O3-0.6Pb(Zn(1/3)Nb(2/3))O3]-0.1PbTiO3, and Pb(Zr(0.52)Ti(0.48))O3, in the mixed oxide compositions and in an amorphous precursor derived from coprecipitation proceeds via a process involving nucleation and subsequent growth of perovskite crystallites with in teasing 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.