Publications by authors named "Fang-Zhou Yao"

Crafting high-performance dielectrics tailored for pulsed power capacitors, in response to the escalating demands of practical applications, presents a formidable challenge. Herein, this work introduces a novel lineup of lead-free ceramics with local polymorphic heterogeneous structures, defined by the formula (1-x)[0.92BaTiO-0.

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Despite the pivotal role of stannum doping in achieving ultrahigh piezoelectric performance in barium titanate-based ceramics, the fundamental mechanisms underlying this enhancement remain elusive. Here, we introduce a single variable nonstoichiometric stannum strategy in lead-free barium titanate-based ceramics with giant piezoelectricity, revealing that stannum doping contributes intrinsically and extrinsically to enhance piezoelectricity. Density functional theory calculations elucidate the intrinsic enhancement of polarization arising from lattice distortion and increased space for titanium-oxygen bonds induced by optimal stannum doping, which is corroborated by Rayleigh analysis.

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High-temperature piezoelectric materials, which enable the accurate and reliable sensing of physical parameters to guarantee the functional operation of various systems under harsh conditions, are highly demanded. To this end, both large piezoelectricity and high Curie temperature are pivotal figures of merit (FOMs) for high-temperature piezoceramics. Unfortunately, despite intensive pursuits, it remains a formidable challenge to unravel the inverse correlation between these FOMs.

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  • Amorphous potassium sodium niobate (KNN) films were created using a sputtering method and then crystallized through annealing at high temperatures in different alkali atmospheres.
  • The post-annealing process allowed for the adjustment of sodium and potassium ratios in the films, influencing their composition and physical properties.
  • Films annealed in high potassium atmospheres showed improved piezoelectric behavior and lower dielectric losses compared to those annealed in high sodium environments, with a specific mixed composition yielding optimal performance in vibration tests.*
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  • * A new strategy using oriented epitaxial self-assembled nanostructures has been proposed to enhance electrostrain and improve polarization vector configuration in Aurivillius-type calcium bismuth niobate (CaBiNbO, CBN) films.
  • * The research confirmed that non-axis oriented CBN films show improved out-of-plane polarization and significant enhancements in ferroelectric performance (∼13.4 μC/cm) and strain (∼0.24%), suggesting promising applications for these films in high-temperature
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Structural health monitoring technology can assess the status and integrity of structures in real time by advanced sensors, evaluate the remaining life of structure, and make the maintenance decisions on the structures. Piezoelectric materials, which can yield electrical output in response to mechanical strain/stress, are at the heart of structural health monitoring. Here, we present an overview of the recent progress in piezoelectric materials and sensors for structural health monitoring.

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Recent advances in perovskite ferroelectrics have fostered a host of exciting sensors and actuators. Defect engineering provides critical control of the performance of ferroelectric materials, especially lead-free ones. However, it remains a challenge to quantitatively study the concentration of defects due to the complexity of measurement techniques.

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Article Synopsis
  • The study focuses on using phase change mechanisms in lead-free piezoceramics to enhance electrostrain through volume changes, specifically in a new (K,Na)NbO solid solution at the polymorphic phase boundary.
  • By combining atomic mapping, synchrotron X-ray diffraction, and density functional theory, researchers identified an electric field-induced phase transition between orthorhombic and tetragonal states, resulting in a significant volume change.
  • This transition contributes to an impressive effective piezoelectric coefficient of 1250 pm V, suggesting greater design flexibility for future high-performance piezoelectric materials.
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Defect engineering is a well-established approach to customize the functionalities of perovskite oxides. In demanding high-power applications of piezoelectric materials, acceptor doping serves as the state-of-the-art hardening approach, but inevitably deteriorates the electromechanical properties. Here, a new hardening effect associated with isolated oxygen vacancies for achieving well-balanced performances is proposed.

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Dielectric capacitors with the prominent features of ultrafast charging-discharging rates and ultrahigh power densities are ubiquitous components in modern electronics. To meet the growing demand for electronics miniaturization, dielectric capacitors with high energy storage properties are extensively researched. Here we present an overview of the recent progress in the engineering of multiscale structures of dielectric ceramics ranging from bulk to thin films.

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Driven by an ever-growing demand for environmentally compatible materials, the past two decades have witnessed the booming development in the field of piezoelectrics. To maximally explore the potential of lead-free piezoelectrics, chemical doping could be an effective approach, referenced from tactics adopted in lead-based piezoelectrics. Herein, we reveal the distinct role of manganese in a promising lead-free perovskite (K, Na)NbO (denoted by KNN) in comparison to that in market-dominating lead-based counterparts [Pb(Zr, Ti)O, PZT].

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La(Co, Cu)O(3-δ) ceramics were prepared by pressureless sintering of citrate precursor powders, and their thermoelectric properties were investigated with an emphasis on the influence of Cu doping and phase structure as well as microstructure. It was found that a secondary phase first appeared in the form of a network along the grain boundaries and then changed to dispersion with increasing Cu content, which effectively reduced the lattice thermal conductivity of the materials. The thermal conductivity was only 1.

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