Lead has recently been expelled from many commercial applications and materials (for example, from solder, glass and pottery glaze) owing to concerns regarding its toxicity. Lead zirconium titanate (PZT) ceramics are high-performance piezoelectric materials, which are widely used in sensors, actuators and other electronic devices; they contain more than 60 weight per cent lead. Although there has been a concerted effort to develop lead-free piezoelectric ceramics, no effective alternative to PZT has yet been found. Here we report a lead-free piezoelectric ceramic with an electric-field-induced strain comparable to typical actuator-grade PZT. We achieved this through the combination of the discovery of a morphotropic phase boundary in an alkaline niobate-based perovskite solid solution, and the development of a processing route leading to highly <001> textured polycrystals. The ceramic exhibits a piezoelectric constant d33 (the induced charge per unit force applied in the same direction) of above 300 picocoulombs per newton (pC N(-1)), and texturing the material leads to a peak d33 of 416 pC N(-1). The textured material also exhibits temperature-independent field-induced strain characteristics.

O 3 polycrystals exhibit piezoelectric properties comparable to those of lead zirconium titanate ceramics which are high-performance piezoelectric materials. The properties of the Pb-free piezoelectric ceramic are due to the existence of a morphotropic phase boundary in the alkaline niobate-based perovskite solid solution. It is expected that the new material is a leading candidate for environmentally friendly piezoelectric devices. -(SAITO, Y.; TAKAO, H.; TANI, T.; NONOYAMA, T.; TAKATORI, K.; HOMMA, T.; NAGAYA, T.; NAKAMURA, M.; Nature (London, UK) 432 (2004) 7013, 84-87; Toyota Cent. Res. Dev. Lab., Nagakute, Aichi 480-11, Japan; Eng.) -W. Pewestorf 03-016

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The microstructural development of crystalline-oriented (K 0.5 Na 0.5 )NbO 3 (KNN)-based piezoelectric ceramics during sintering was investigated. The addition of CuO as a sintering aid was found to be effective for fabricating highly oriented and dense KNN ceramics. KNN specimens containing 0.5-1.0 mol% CuO sintered at 11001C for 1 h were found to have relative densities and pseudo-cubic {100} orientation degrees of 95% or higher. In the early stages of sintering, KNN is formed in the reaction between complementary reactants NaNbO 3 and KNbO 3 , after which oriented grain growth proceeds at a relative density of more than 90%. In addition, the results of transmission electron microscopy observation showed that textured KNN ceramics have a unique pectinate-like domain structure with domain walls consisting of {101} planes. 1951J ournal

Dense CaBi4Ti4O15 (CBT) and Na0.475Ca0.05Bi4.475Ti4O15 (NCBT) ceramics with a highly preferred {001} orientation were prepared by the reactive templated grain growth (RTGG) method. Plate-like Bi4Ti3O12 (BIT) particles were synthesized by a molten salt technique and used as the reactive template. The template particles were mixed with other oxide and carbonate powders and aligned by tape-casting. During the sintering, oriented CBT and NCBT were formed in situ topotaxially on the oriented BIT particles, and textured CBT and NCBT ceramics were eventually fabricated by the templated grain growth and densification. The Lotgering {001} orientation degree of the textured ceramics exceeded 90% for secondary-laminate sintered specimens. Textured CBT and NCBT ceramics poled in the perpendicular direction to the preferred <001> axis exhibited electromechanical coupling coefficient (k 33) and piezoelectric coefficients (d 33 and g 33) three times higher than the values for nontextured ceramics with the same composition.