Lead-free piezoceramics

Abstract

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.

Hallmarks of mechanochemistry: from nanoparticles to technology

“…17b). This is supported by the XRD analysis (not shown): at room temperature the conventionally prepared KNLNT is orthorhombic, 306 whereas the mechanochemically prepared KNLNT could be indexed with the tetragonal structure, 295 in agreement with the original paper by Saito et al 274 The observed different T O-T (50 1C) in the conventionally processed KNLNT is probably related to the Ta inhomogeneities, e.g. incomplete incorporation of Ta into the solid solution and presence of Ta-poor(rich) regions with different T O-T (see Fig.…”

“…271,272 So far, the (K,Na)NbO 3 (KNN) solid solution has been one of the most studied among the alternatives. 273 The research on KNN was reinforced in 2004 by the paper of Saito et al, 274 who showed that piezoelectric properties comparable to PZT could be achieved by modifying KNN with Li, Ta and Sb, or by grain orientation (texturing). However, the high piezoelectricity of these materials originates from the enhanced polarizability associated with the compositional shift of the orthorhombicto-tetragonal polymorphic phase transition (PPT) from 195 1C for pure KNN 275 downward to room temperature.…”

Synthesis of Barium Titanate Using Deep Eutectic Solvents

“…(1-x)(BaTiO3) 9 or x(NaNbO3). (1-x)(BaTiO3) 39 for potential high temperature capacitor applications. The method circumvents the issue of poor mixing of oxide or carbonate precursors in conventional mixed oxide routes, with starting materials being homogeneously distributed from the outset.…”

Unusual Phase Behavior in the Piezoelectric Perovskite System, LixNa1–xNbO3

“…1 A leading candidate amongst a range of promising materials is the solid solution KNN (K x Na 1-x NbO 3 ). 2,3 Sodium niobate (NaNbO 3 ) itself is an intriguing material, with perhaps one of the most complex temperature-dependent phase diagrams amongst simple perovskites. 4 , 5 , 6 Although itself antiferroelectric (orthorhombic, Phase P, space group Pbcm) at ambient temperature, NaNbO 3 becomes ferroelectric (rhombohedral, Phase N, space group R3c, Glazer tilt system 7 a -a -a -) below 173 K. Depending on sample synthesis conditions, a ferroelectric polymorph, Phase Q (orthorhombic, space group P2 1 ma, Glazer tilt system a -b + a -) can co-exist with Phase P at room temperature.…”