Next‐generation electronics and energy technologies can now be developed as a result of the design, discovery, and development of novel, environmental friendly lead (Pb)‐free ferroelectric materials with improved characteristics and performance. However, there have only been a few reports of such complex materials’ design with multi‐phase interfacial chemistry, which can facilitate enhanced properties and performance. In this context, herein, novel lead‐free piezoelectric materials (1‐
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In many commercially utilized ferroelectric materials, the motion of domain walls is an important contributor to the functional dielectric and piezoelectric responses. This paper compares the temperature dependence of domain wall motion for BaTiO3 ceramics with different grain sizes, point defect concentrations, and formulations. The grain boundaries act as significant pinning points for domain wall motion such that fine-grained materials show smaller extrinsic contributions to the properties below the Curie temperature and lower residual ferroelectric contributions immediately above the Curie temperature. Oxygen vacancy point defects make a modest change in the extrinsic contributions of undoped BaTiO3 ceramics. In formulated BaTiO3, extrinsic contributions to the dielectric response were suppressed over a wide temperature range. It is believed this is due to a combination of reduced grain size, the existence of a core-shell microstructure, and a reduction in domain wall continuity over the grain boundaries.
more » « less- NSF-PAR ID:
- 10480943
- Publisher / Repository:
- OAE Publishing
- Date Published:
- Journal Name:
- Microstructures
- Volume:
- 3
- Issue:
- 4
- ISSN:
- 2770-2995
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract x )Ba0.95Ca0.05Ti0.95Zr0.05O3‐(x )Ba0.95Ca0.05Ti0.95Sn0.05O3, are reported, which are represented as (1‐x )BCZT‐(x )BCST, with demonstrated excellent properties and energy harvesting performance. The (1‐x )BCZT‐(x )BCST materials are synthesized by high‐temperature solid‐state ceramic reaction method by varyingx in the full range (x = 0.00–1.00). In‐depth exploration research is performed on the structural, dielectric, ferroelectric, and electro‐mechanical properties of (1‐x )BCZT‐(x )BCST ceramics. The formation of perovskite structure for all ceramics without the presence of any impurity phases is confirmed by X‐ray diffraction (XRD) analyses, which also reveals that the Ca2+, Zr4+, and Sn4+are well dispersed within the BaTiO3lattice. For all (1‐x )BCZT‐(x )BCST ceramics, thorough investigation of phase formation and phase‐stability using XRD, Rietveld refinement, Raman spectroscopy, high‐resolution transmission electron microscopy (HRTEM), and temperature‐dependent dielectric measurements provide conclusive evidence for the coexistence of orthorhombic + tetragonal (Amm2 +P4mm ) phases at room temperature. The steady transition ofAmm2 crystal symmetry toP4mm crystal symmetry with increasingx content is also demonstrated by Rietveld refinement data and related analyses. The phase transition temperatures, rhombohedral‐orthorhombic (TR‐O), orthorhombic‐ tetragonal (TO‐T), and tetragonal‐cubic (TC), gradually shift toward lower temperature with increasingx content. For (1‐x )BCZT‐(x )BCST ceramics, significantly improved dielectric and ferroelectric properties are observed, including relatively high dielectric constantε r≈ 1900–3300 (near room temperature),ε r≈ 8800–12 900 (near Curie temperature), dielectric loss, tanδ ≈ 0.01–0.02, remanent polarizationP r≈ 9.4–14 µC cm−2, coercive electric fieldE c≈ 2.5–3.6 kV cm−1. Further, high electric field‐induced strainS ≈ 0.12–0.175%, piezoelectric charge coefficientd 33≈ 296–360 pC N−1, converse piezoelectric coefficient ≈ 240–340 pm V−1, planar electromechanical coupling coefficientk p≈ 0.34–0.45, and electrostrictive coefficient (Q 33)avg≈ 0.026–0.038 m4C−2are attained. Output performance with respect to mechanical energy demonstrates that the (0.6)BCZT‐(0.4)BCST composition (x = 0.4) displays better efficiency for generating electrical energy and, thus, the synthesized lead‐free piezoelectric (1‐x )BCZT‐(x )BCST samples are suitable for energy harvesting applications. The results and analyses point to the outcome that the (1‐x )BCZT‐(x )BCST ceramics as a potentially strong contender within the family of Pb‐free piezoelectric materials for future electronics and energy harvesting device technologies. -
The BaTiO3 ceramics applications based on electronic properties have very high gradient scientific and industrial-technological interests. Our scientific research has been based on nano BaTiO3 modified with Yttrium based organometallic salt (MOD-Y). The samples have been consolidated at a sintering temperature of 1350 °C. Within the study, the new frontiers for different electronic properties between the layers of BaTiO3 grains have been introduced. The research target was grain boundary investigations and the influence on dielectric properties. After scanning electron microscopy and dielectric measurements, it has been established that modified BaTiO3 samples with larger grains showed a better compact state that led to a higher dielectric constant value. DC bias stability was also investigated and showed a connection between the grain size and capacitance stability. Analyses of functions that could approximate experimental curves were successfully employed. Practical application of fractal corrections was performed, based on surface (αs) and pore size (αp) corrections, which resulted in obtainment of the relation between the capacitance and Curie temperature. Successful introduction of fractal corrections for capacitance-Curie temperature dependence for a set of experimental data is an important step towards further miniaturization of intergranular capacitors.more » « less
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Ferroelectric materials such as barium titanate (BaTiO3) have a wide range of applications in nano scale electronic devices due to their outstanding properties. In this study, we developed an easily extendable atomistic ReaxFF reactive force field for BaTiO3 that can capture both its field- as well as temperature-induced ferroelectric hysteresis and corresponding changes due to surface chemistry and bulk defects. Using our force field, we were able to reproduce and explain a number of experimental observations: (1) existence of a critical thickness of 4.8 nm below which ferroelectricity vanishes in BaTiO3; (2) migration and clustering of oxygen vacancies (OVs) in BaTiO3 and reduction in the polarization and the curie temperature due to the OVs; (3) domain wall interaction with surface chemistry to influence ferroelectric switching and polarization magnitude. This new computational tool opens up a wide range of possibilities for making predictions for realistic ferroelectric interfaces in energy-conversion, electronic and neuromorphic systems.more » « less
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Pyroelectric materials, are those materials with the property that in the absence of any externally applied electric field, develop a built-in spontaneous polarization in their unit cell structure. They are regarded as ideal detector elements for infrared applications because they can provide fast response time and uniform sensitivity at room temperature over all wavelengths. Crystals of the perovskite Lead Titanate (PbTiO3) family show pyroelectric characteristics and undergo structural phase transitions. They have a high Curie temperature (the temperature at which the material changes from the ferroelectric (polar) to the paraelectric (nonpolar) phase), high pyroelectric coefficient, high spontaneous polarization, low dielectric constant, and constitute important component materials not only useful for infrared detection, but also with vast applications in electronic, optic, and Micro-electromechanical systems (MEMS) devices. However, the preparation of large perfect, and pure single crystals of PbTiO3 is challenging. Additionally, difficulties arise in the application of such bulk crystals in terms of connection to processing circuits, large size, and high voltages required for their operation. A number of thin film fabrication techniques have been proposed to overcome these inadequacies, among which, magnetron sputtering has demonstrated many potentials. By addressing these aspects, the review article aims to contribute to the understanding of the challenges in the field of pyroelectric materials, highlight potential solutions, and showcase the advancements and potentials of pyroelectric perovskite series including PbZrTiO3 (PZT), PbxCa1−x (PZN-PT), etc. for which PbTiO3 is the end member. The review is presented in two parts. Part 1 focuses on material aspects, including preparation methods using magnetron sputtering and material characterization. We take a tutorial approach to discuss the progress made in epitaxial growth of lead titanate-based ceramics prepared by magnetron sputtering and examine how processing conditions may affect the crystalline quality of the growing film by linking to the properties of the substrate/buffer layer, growth substrate temperature, and the oxygen partial pressure in the gas mixture. Careful control and optimization of these parameters are crucial for achieving high-quality thin films with desired structural and morphological characteristics.
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Abstract Though ferroelectric HfO2thin films are now well characterized, little is currently known about their grain substructure. In particular, the formation of domain and phase boundaries requires investigation to better understand phase stabilization, switching, and phase interconversion. Here, scanning transmission electron microscopy is applied to investigate the atomic structure of boundaries in these materials. It is found that orthorhombic/orthorhombic domain walls and coherent orthorhombic/monoclinic interphase boundaries form throughout individual grains. The results inform how interphase boundaries can impose strain conditions that may be key to phase stabilization. Moreover, the atomic structure near interphase boundary walls suggests potential for their mobility under bias, which has been speculated to occur in perovskite morphotropic phase boundary systems by mechanisms similar to domain boundary motion.
