Growth of Pb(Mg1/3Nb2/3)O-3-35 mol% PbTiO3 single crystals from (111) substrates by seeded polycrystal conversion

Fully dense disks, each consisting of a single crystal (111) plate of the r elaxer-based ferroelectric Pb(Mg1/3Nb2/3)O-3-35 mol% PbTiO3 (PMN-35PT) embe dded in a 0.48 +/- 0.05 pm grain size polycrystalline matrix of the same co mposition, were formed by hot-pressing at 950 degrees C for 30 min under 20 MPa. Specimens were subsequently annealed to promote migration of the sing le-crystal boundary through the polycrystal (a process termed seeded polycr ystal conversion). An anneal of 10 h at 1150 degrees C using PMN-35PT packi ng powder resulted in minimal single-crystal boundary migration, and was ac companied by matrix grain coarsening to 1.86 +/- 0.20 pm, In contrast, an a nneal of 10 h at 1150 degrees C using PbZrO3 (PZ) sacrificial powder result ed in significant migration of the single-crystal boundary through the poly crystal, accompanied by matrix grain coarsening to 13.3 +/- 0.3 pm. The sha pe of the grown crystal relative to the seed plate was consistent with the [111] direction being the fastest growth direction. Based on the grown crys tal dimensions, a lower bound [111] growth velocity of 0.14 mm/h was calcul ated. The increased boundary mobility in the specimen that was annealed usi ng PZ sacrificial powder is attributed to a boundary-wetting liquid PbO-bas ed second phase that formed during the anneal. This phase is believed to ha ve formed via PbO absorption from the surrounding vapor phase due to a high er equilibrium PbO vapor pressure above PZ than above PMN-35PT. The grown s ingle crystal exhibited a promising [100] strain of 0.5% at an applied elec tric field of 4 MV/m.