Impact of stress-induced precipitate variant selection on anisotropic electrical properties of piezoceramics.

Precipitation hardening has been recently validated as a new mechanism for domain wall pinning and mechanical loss reduction in piezoelectrics. While anisometric precipitates have high pinning strengths, there is limited knowledge about the electrical anisotropy of the precipitation-hardened piezoceramics. In the present work, we successfully orient the precipitates in LiNaNbO piezoceramics by applying a uniaxial stress during the aging and studied its electrical anisotropy.

Fundamental workings of chemical substitution at the A-site of perovskite oxides- a Pb NMR study of Ba-substituted PbZrO.

Lead zirconate (PbZrO, PZ) is a prototype antiferroelectric (AFE) oxide from which state-of-the-art energy storage materials are derived by chemical substitutions. A thorough understanding of the structure-property relationships of PZ-based materials is essential for both performance improvement and the design of more environmentally friendly replacements. (PbBa)ZrO (PBZ) can serve as a model system for studying the effect of A-site substitution in the perovskite lattice, with barium destabilizing the AFE state.

Anisotropic dislocation-domain wall interactions in ferroelectrics.

Dislocations are usually expected to degrade electrical, thermal and optical functionality and to tune mechanical properties of materials. Here, we demonstrate a general framework for the control of dislocation-domain wall interactions in ferroics, employing an imprinted dislocation network. Anisotropic dielectric and electromechanical properties are engineered in barium titanate crystals via well-controlled line-plane relationships, culminating in extraordinary and stable large-signal dielectric permittivity (≈23100) and piezoelectric coefficient (≈2470 pm V).

Coherent Precipitates with Strong Domain Wall Pinning in Alkaline Niobate Ferroelectrics.

High-power piezoelectric applications are predicted to share approximately one-third of the lead-free piezoelectric ceramic market in 2024 with alkaline niobates as the primary competitor. To suppress self-heating in high-power devices due to mechanical loss when driven by large electric fields, piezoelectric hardening to restrict domain wall motion is required. In the present work, highly effective piezoelectric hardening via coherent plate-like precipitates in a model system of the (Li,Na)NbO (LNN) solid solution delivers a reduction in losses, quantified as an electromechanical quality factor, by a factor of ten.

Measurement System for Piezoelectric Resonance Impedance Spectroscopy Under Combined AC and High-Voltage DC Loading.

Piezoelectric resonance impedance spectroscopy is a standardized measurement technique for determining the electromechanical, elastic, and dielectric parameters of piezoceramics. However, commercial measurement setups are designed for small-signal measurements and encounter difficulties when constant driving voltages/currents are required at resonances, higher fields, or combined AC and DC loading. The latter is particularly important to evaluate the DC bias-hardening effect of piezoelectrics.

Precipitation Hardening in Ferroelectric Ceramics.

Domain wall motion in ferroics, similar to dislocation motion in metals, can be tuned by well-concepted microstructural elements. In demanding high-power applications of piezoelectric materials, the domain wall motion is considered as a lossy hysteretic mechanism that should be restricted. Current applications for so-called hard piezoelectrics are abundant and hinge on the use of an acceptor-doping scheme.

Control of polarization in bulk ferroelectrics by mechanical dislocation imprint.

Defects are essential to engineering the properties of functional materials ranging from semiconductors and superconductors to ferroics. Whereas point defects have been widely exploited, dislocations are commonly viewed as problematic for functional materials and not as a microstructural tool. We developed a method for mechanically imprinting dislocation networks that favorably skew the domain structure in bulk ferroelectrics and thereby tame the large switching polarization and make it available for functional harvesting.

Polarization Rotation at Morphotropic Phase Boundary in New Lead-Free NaBiVTiO Piezoceramics.

In this work, we show that polarization rotation enhances the piezoresponse in a high-performance lead-free piezoelectric material, NaBiVTiO, a solid solution between tetragonal NaBiVO and rhombohedral NaBiTiO, obtained by high-pressure synthesis. The system forms a pure perovskite structure with a favorable morphotropic phase boundary (MPB) located around = 0.90, which separates the tetragonal and rhombohedral phases.

Ferroelastic Properties of PZT: Characterization Under Compressive and Tensile Stress, Finite-Element Simulation, and Lifetime Calculation.

Finite-element (FE) simulations, based on a phenomenological nonlinear constitutive model, were carried out to show the impact of ferroelastic switching on compressive and tensile loading of a soft and hard ferroelastic polycrystalline lead zirconate titanate ceramic (PbZr1-xTixO3, PZT). Hereby, a model assembly is used that simulates mechanical stresses generated by the contact of a ceramic element with a concave counterpart. In order to parameterize the constitutive model, the elastic and piezoelectric tensors are determined by the small signal resonance method and by the direct measurement under compressive/tensile loads.

Temperature-Dependent Evolution of Crystallographic and Domain Structures in (K,Na,Li)(Ta,Nb)O3 Piezoelectric Single Crystals.

(K,Na)NbO3-based ferroelectric single crystals have recently undergone a substantial development, resulting in improved crystal quality and large piezoelectric coefficients, exceeding 700 pC/N, over a broad temperature range. However, further development necessitates a detailed understanding of the mechanisms defining the domain structure and its temperature evolution. This paper presents the investigation into the crystallographic structure and domain configurations of a (K,Na,Li)(Ta,Nb)O3 single crystal over a broad temperature range.

Inverted electro-mechanical behaviour induced by the irreversible domain configuration transformation in (K,Na)NbO3-based ceramics.

Miniaturization of domains to the nanometer scale has been previously reported in many piezoelectrics with two-phase coexistence. Despite the observation of nanoscale domain configuration near the polymorphic phase transition (PPT) regionin virgin (K0.5Na0.

Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics.

The potassium sodium niobate, KNaNbO₃, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics.

Enhancing electromechanical properties of lead-free ferroelectrics with bilayer ceramic/ceramic composites.

The macroscopic electromechanical behavior of lead-free bilayer composites was characterized at room temperature. One layer consisted of a nonergodic relaxor, (Bi1/2Na1/2)TiO3-7BaTiO3, with an electric-field-induced longrange ferroelectric order, whereas the other is understood to be an ergodic relaxor [(Bi1/2Na1/2)TiO3-25SrTiO3] that undergoes a reversible electric-field-induced macroscopic nonpolar-to-polar transition. Microstructural evidence of a bilayer with low diffusion between the two components is also demonstrated.

Electric-field-induced phase transitions in co-doped Pb(ZrTi)O at the morphotropic phase boundary.

The strain- and polarization-electric field behavior was characterized at room temperature for PbBa(Zr Ti )NbO, 0.40 ⩽ ⩽ 0.60.