Crystallographic texturing of polycrystalline ferroelectric ceramics offers a means of achieving significant enhancements in the piezoelectric response. Templated grain growth (TGG) enables the fabrication of textured ceramics with single crystal-like properties, as well as single crystals. In TGG, nucleation and growth of the desired crystal on aligned single crystal template particles results in an increased fraction of oriented material with heating. To facilitate alignment during forming, template particles must be anisometric in shape. To serve as the preferred sites for epitaxy and subsequent oriented growth of the matrix, the template particles need to be single crystal and chemically stable up to the growth temperature. Besides templating the growth process, the template particles may also serve as seed sites for phase formation of a reactive matrix. This process, referred to as Reactive TGG (RTGG), has been used to obtain highly oriented Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃, Sr_0.53Ba_0.47Nb₂O₆, and (Na_1/2Bi_1/2)TiO₃-BaTiO₃. Highly oriented Bi₄Ti₃O₁₂, Sr₂Nb₂O₇, CaBi₄Ti₄O₁₅, Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃, Sr_0.53Ba_0.47Nb₂O₆ and (Na_1/2Bi_1/2)TiO₃-BaTiO₃ ceramics have been produced by TGG. The resulting ceramics show texture levels up to 90%, and significant enhancements in the piezoelectric properties relative to randomly oriented ceramics with comparable densities. For example, piezoelectric coefficients of textured piezoelectrics are from 2 to 3 times higher than polycrystalline ceramics and as high as 90% of the single crystal values. In textured PMN-PT, a low field (< 5 kV/cm) piezoelectric coefficient (d ₃₃) of ∼1600 pC/N was obtained with > 0.3% strain (at 50 kV/cm). The high field dielectric and electromechanical properties of textured perovskites are more hysteretic than those of single crystals, probably as a result of clamping by the residual template particles, residual random grains, the presence of non-ferroelectric second phases, and a wide orientation distribution. Lateral clamping of one grain by another may also be an important factor in fiber-textured samples. Means to further improve the quality of texture and thus properties of textured piezoelectric ceramics by TGG are presented.

The piezoelectric properties of $\text{(1−x)}$ ${\mathrm{Pb(Mg}}_{\mathrm{1/3}}{\mathrm{Nb}}_{\mathrm{2/3}}{\mathrm{)O}}_3\mathrm{–x}{\mathrm{PbTiO}}_3$ $\text{(x=0.3–0.35),}$ ceramics with a high degree of 〈001〉 fiber texture were investigated for possible actuator applications. Piezoelectric coefficients ${\mathrm{(d}}_{33})$ in excess of 1200 pC/N associated with strain levels up to >0.3% were observed in samples prepared by a reactive templated grain growth process. No excess PbO was used in the starting composition. A high degree of fiber texture was achieved using 〈001〉 oriented ${\mathrm{BaTiO}}_3$ template particles in a fine-grained precursor for the PMN–32PT matrix. High densities together with texture resulted in a significant increase in strain levels and $d_{33}$ values compared to their polycrystalline counterparts. Peak dielectric constants on the order of 22 000 with losses of ∼2% and well-saturated hysteresis loops with a $P_r\text{∼27\hspace{0.5em}μ}{\mathrm{C/cm}}^2$ were recorded on the textured samples. These domain engineered, textured ceramics have tremendous potential for high-performance actuators.

The $\text{0.675}\mathrm{Pb}({\mathrm{Mg}}_{\text{1/3}}{\mathrm{Nb}}_{\text{2/3}}){\mathrm{O}}_3\text{–0.325}{\mathrm{PbTiO}}_3$ (PMN–32.5PT) ceramic composition (with 1 wt. % excess PbO) was fiber textured in the 〈001〉 direction by the templated grain growth process using 5 vol % oriented $\text{{001}-}{\mathrm{BaTiO}}_3$ platelet crystals as the templates. The templated ceramics annealed at $\text{1150\hspace{0.05em}°}\mathrm{C}$ for 5 h attained texture fractions as high as 0.9. The fiber-textured samples showed an increase in the piezoelectric, electromechanical coupling, and compliance coefficients when poled and measured in the 〈001〉-textured direction. The low drive field $\text{(<5\hspace{0.17em}}\mathrm{kV/cm})$ $d_{33}$ coefficients in the 〈001〉, measured directly from unipolar strain-field measurements, were $\text{∼1150\hspace{0.17em}}\mathrm{pC/N}.$ This $d_{33}$ coefficient is 1.2–1.5 times greater than randomly oriented samples. The poled ${\epsilon }_{\max }$ and ${\epsilon }_{\mathrm{rt}}$ for a 0.9-textured PMN–32.5PT ceramic were 21 500 and 2450, respectively. Factors limiting further property improvements are discussed.

Cerium oxide (CeO₂) nanoparticles, which are used in a variety of products including solar cells, gas sensors, and catalysts, are expected to increase in industrial use. This will subsequently lead to additional occupational exposures, making toxicology screenings crucial. Previous toxicology studies have presented conflicting results as to the extent of CeO₂ toxicity, which is hypothesized to be due to the ability of Ce to exist in both a +3 and +4 valence state. Thus, to study whether valence state and oxygen vacancy concentration are important in CeO₂ toxicity, CeO₂ nanoparticles were doped with gadolinium to adjust the cation (Ce, Gd) and anion (O) defect states. The hypothesis that doping would increase toxicity and decrease antioxidant abilities as a result of increased oxygen vacancies and inhibition of +3 to +4 transition was tested. Differences in toxicity and reactivity based on valence state were determined in RLE-6TN rat alveolar epithelial and NR8383 rat alveolar macrophage cells using enhanced dark field microscopy, electron paramagnetic resonance (EPR), and annexin V/propidium iodide cell viability stain. Results from EPR indicated that as doping increased, antioxidant potential decreased. Alternatively, doping had no effect on toxicity at 24 h. The present results imply that as doping increases, thus subsequently increasing the Ce³⁺/Ce⁴⁺ ratio, antioxidant potential decreases, suggesting that differences in reactivity of CeO₂ are due to the ability of Ce to transition between the two valence states and the presence of increased oxygen vacancies, rather than dependent on a specific valence state.