Growth of Pb(Mg1/3Nb2/3)O3‐35 mol% PbTiO3 Single Crystals from (111) Substrates by Seeded Polycrystal Conversion

Abstract

Fully dense disks, each consisting of a single crystal (111) plate of the relaxor‐based ferroelectric Pb(Mg1/3Nb2/3)O3‐35 mol% PbTiO3 (PMN‐35PT) embedded in a 0.48 ± 0.05 µm grain size polycrystalline matrix of the same composition, were formed by hot‐pressing at 950°C for 30 min under 20 MPa. Specimens were subsequently annealed to promote migration of the single‐crystal boundary through the polycrystal (a process termed seeded polycrystal conversion). An anneal of 10 h at 1150°C using PMN‐35PT packing powder resulted in minimal single‐crystal boundary migration, and was accompanied by matrix grain coarsening to 1.86 ± 0.20 µm. In contrast, an anneal of 10 h at 1150°C using PbZrO3 (PZ) sacrificial powder resulted in significant migration of the single‐crystal boundary through the polycrystal, accompanied by matrix grain coarsening to 13.3 ± 0.3 µm. The shape of the grown crystal relative to the seed plate was consistent with the <111> direction being the fastest growth direction. Based on the grown crystal dimensions, a lower bound <111> growth velocity of 0.14 mm/h was calculated. The increased boundary mobility in the specimen that was annealed using PZ sacrificial powder is attributed to a boundary‐wetting liquid PbO‐based second phase that formed during the anneal. This phase is believed to have formed via PbO absorption from the surrounding vapor phase due to a higher equilibrium PbO vapor pressure above PZ than above PMN‐35PT. The grown single crystal exhibited a promising <100> strain of 0.5% at an applied electric field of 4 MV/m.

Growth mechanism of relaxor-PbTiO3 single crystals shown by morphology of crystalline grains in ceramics

“…So far it is widely accepted that the {1 0 0} plane has the lowest growth rate, and growth along the /1 1 1S directions is the fastest [10,12,[24][25][26]. However, it is still uncertain whether the growth of {1 1 0} or {1 1 1} faces have contributed to the 3D morphology of grown single crystals [12].…”

“…4(a)), resulting from the convergence of advancing layers on three growth faces sharing the same corner. This implies that the crystal growth in the /1 1 1S directions, which was regarded in the past to have the fastest growth rate [24][25][26], is actually consequent on the growth of three surrounding {1 0 0} faces.…”

Anisotropic Laminar Piezocomposite Actuator Incorporating Machined PMN–PT Single-crystal Fibers

“…The recent progress in high performance single-crystal piezoelectric materials (Park and Shrout, 1997;Li, et al, 1998;Khan, et al, 1999) may permit even greater stress and strain output when used in interdigitated piezocomposites. Single-crystal piezoelectric materials are effectively contiguous macrocrystals, grown layer by layer to yield an individual crystal consisting of only single atoms repeating in a specific structural pattern.…”

Application of spark plasma sintering for growing dense Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 single crystal by solid-state crystal growth

“…Therefore, a more economical procedure in which single crystal seed is embedded in the polycrystalline precursor was introduced. [6,7]. During heat-treatment, the seed crystal may grow by a capillary driving force with the consumption of small matrix grains.…”