| Rhombohedral Pb(Mg1/3Nb2/3)O3-PbTiO 3 (PMN-PT) single crystals near the morphotropic phase boundary (MPB) show enhanced strain levels combined with exceedingly large piezoelectric and electromechanical coupling coefficients for ⟨001⟩-oriented and -poled crystal cuts. In principle, ⟨001⟩ fiber-textured PMN-PT ceramics should possess a high fraction of the electromechanical and dielectric properties displayed by their single crystal counterparts. To investigate this, the Templated Grain Growth (TGG) process was used to fiber-texture PMN-PT in the ⟨001⟩ direction. The TGG process involves the growth of multiple oriented template particles into a fine-grained matrix during thermal processing.; Potential template particles with a layered-perovskite and tungsten-bronze structure (Bi4Ti3O12, Sr3Ti 2O7, KSr2Nb5O15, and Sr 2Nb2O7) were shown to form a cubic-pyrochlore phase when reacted with the PMN-PT matrix at temperatures >850°C. The BaTiO3 crystals were stable within the PMN-PT matrix at temperatures >850°C and they were shown to act as proper heteroepitaxial substrates for templated growth of the PMN-PT composition.; The TGG kinetics from {lcub}001{rcub}-, {lcub}110{rcub}-, and {lcub}111{rcub}-BaTiO 3 crystals were observed and fitted to a diffusion-controlled model with a non-constant driving force. The crystal growth kinetics were shown to be limited by the decrease in the driving force due to the coarsening and shape change of the matrix grains.; PMN-32.5PT ceramics were fiber-textured by initially aligning {lcub}001{rcub}-BaTiO 3 platelets (∼75–150 μm in diameter) within the matrix by tapecasting. Dense PMN32.5PT ceramics (1 wt% excess PbO) with a 5 vol% template concentration were ⟨001⟩ textured to a texture fraction ∼0.90 with an annealing time >1 h at 1150°C.; An increase in texture fraction of the {lcub}001{rcub}-BaTiO3 templated PMN-32.5PT ceramics produced an increase in the piezoelectric, electromechanical coupling, and compliance coefficients over randomly-oriented samples of the same composition. The d33 coefficient of highly textured PMN-32.5PT ceramics (∼90%-textured) were found to be ∼1.2–1.5 times greater than randomly-oriented samples. The magnitude of the dielectric and piezoelectric properties were also found to be limited by the presence of misoriented templated-grains, unoriented grains, porosity, and the remnant BaTiO3 templates. (Abstract shortened by UMI.)... |
