Seeding of perovskite lead magnesium niobate crystallization from Pb-Mg-Nb-EDTA gels

The addition of BaTiO₃ seed particles (50 nm in diameter) to a Pb-Mg-Nb-EDTA solution (where EDTA represents ethylenediamine tetraacetic acid) reduces the formation temperature from 700°C to 600°C during combustion synthesis, because of epitaxial effects. The lower perovskite formation temperature eliminates the formation of pyrochlore at the surface of the precursor bed and allows for the direct crystallization of approx. 98% perovskite lead magnesium niobate (PMN) during combustion synthesis. Increasing the nucleation density of the seed particles in the seeded precursor decreases the precursor volume that is associated with each perovskite nucleus and, thus, reduces the PMN particle size from 1 μm to 0.2 μm. The influence of BaTiO₃ seeding is discussed in terms of the thermodynamics of perovskite formation, the influence of BaTiO₃ seed concentration, and epitaxial nucleation.