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Author: Maryam Abazari Torghabeh
Publisher:
ISBN:
Category : Ferroelectric devices
Languages : en
Pages : 193
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Book Description
As a high performance piezoelectric material widely used in sensors, actuators and other electronic devices, lead zirconate titanate (PZT) ceramics have been the center of attention for many years. However, the toxicity of these materials and their exposure to the environment during processing steps, such as calcination, sintering, machining as well as problems in recycling and disposal have been major concerns regarding their usage all around the globe for the past couple of decades. Consequently, utilizing lead-based materials for many commercial applications have been recently restricted in Europe and Asia and measures are being taken in United States as well. Therefore, there is an urgent need for lead-free piezoelectrics whose properties are comparable to those of well-known PZT materials. Recently, the discovery of ultra-high piezoelectric activity in the ternary lead-free KNaNbO3-LiTaO3-LiSbO3 (KNN-LT-LS) and (Bi, Na)TiO3-(Bi, K)TiO3-BaTiO3 (BNT-BKT-BT) systems have given hope for alternatives to PZT. Furthermore, the demand for new generation of environment-friendly functional devices, utilizing piezoelectric materials, inspired a new surge in lead-free piezoelectric thin film research. In this study, an attempt has been made to explore the development of lead-free piezoelectric thin films by Pulsed Laser Deposition (PLD) on SrTiO3 substrate. While the growth and development process of KNN-LT-LS thin films was the primary goal of this thesis, a preliminary effort was also made to fabricate and characterize BNT-BKT-BT thin films. In a comprehensive and systematic process optimization study in conjunction with X-ray diffractometry, the phase evolution, stoichiometry, and growth orientation of the films are monitored as a function of deposition conditions including temperature and ambient oxygen partial pressure. Processing parameters such as substrate temperature and pressure are shown to be highly dominant in determining the phase and composition of the films. Oxygen partial pressure has shown to control the chemical composition of the films through solid-gaseous phase equilibrium and substrate temperature has mostly influenced the growth mode and microstructure. Findings of this study has shown that 300-500 nm single-phase epitaxial KNN-LT-LS and BNT-BKT-BT thin films could indeed be obtained at a temperature of 700-750 oC and 300-400 mTorr of oxygen partial pressure. Following a series of studies on effect of doping, it was revealed that addition of 1 mol% Mn to KNN-LT-LS composition resulted in a significant suppression of leakage current and enhancement of polarization saturation. A remanent polarization of 16 æC/cm2 and coercive field of 20 kV/cm were measured for such thin film, which are comparable to those of hard PZT counterparts. Also, a high remanent polarization and coercive field of 30 æC/cm2 and 95 kV/cm were achieved in 350 nm BNT-BKT-BT thin films. Longitudinal (d33) and transverse (e31, f) piezoelectric coefficients of KNN-LT-LS thin films were found to be 55 pm/V and -4.5 C/m2 respectively, prepared at the optimized conditions, whereas 350 nm BNT-BKT-BT thin films exhibited an e31, f of -2.25 C/m2. The results of this study present the great potential of KNN-LT-LS and BNT-BKT-BT thin films for piezoelectric MEMS devices and provide a baseline for future investigations on lead-free piezoelectric thin films.
Author: Maryam Abazari Torghabeh
Publisher:
ISBN:
Category : Ferroelectric devices
Languages : en
Pages : 193
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Book Description
As a high performance piezoelectric material widely used in sensors, actuators and other electronic devices, lead zirconate titanate (PZT) ceramics have been the center of attention for many years. However, the toxicity of these materials and their exposure to the environment during processing steps, such as calcination, sintering, machining as well as problems in recycling and disposal have been major concerns regarding their usage all around the globe for the past couple of decades. Consequently, utilizing lead-based materials for many commercial applications have been recently restricted in Europe and Asia and measures are being taken in United States as well. Therefore, there is an urgent need for lead-free piezoelectrics whose properties are comparable to those of well-known PZT materials. Recently, the discovery of ultra-high piezoelectric activity in the ternary lead-free KNaNbO3-LiTaO3-LiSbO3 (KNN-LT-LS) and (Bi, Na)TiO3-(Bi, K)TiO3-BaTiO3 (BNT-BKT-BT) systems have given hope for alternatives to PZT. Furthermore, the demand for new generation of environment-friendly functional devices, utilizing piezoelectric materials, inspired a new surge in lead-free piezoelectric thin film research. In this study, an attempt has been made to explore the development of lead-free piezoelectric thin films by Pulsed Laser Deposition (PLD) on SrTiO3 substrate. While the growth and development process of KNN-LT-LS thin films was the primary goal of this thesis, a preliminary effort was also made to fabricate and characterize BNT-BKT-BT thin films. In a comprehensive and systematic process optimization study in conjunction with X-ray diffractometry, the phase evolution, stoichiometry, and growth orientation of the films are monitored as a function of deposition conditions including temperature and ambient oxygen partial pressure. Processing parameters such as substrate temperature and pressure are shown to be highly dominant in determining the phase and composition of the films. Oxygen partial pressure has shown to control the chemical composition of the films through solid-gaseous phase equilibrium and substrate temperature has mostly influenced the growth mode and microstructure. Findings of this study has shown that 300-500 nm single-phase epitaxial KNN-LT-LS and BNT-BKT-BT thin films could indeed be obtained at a temperature of 700-750 oC and 300-400 mTorr of oxygen partial pressure. Following a series of studies on effect of doping, it was revealed that addition of 1 mol% Mn to KNN-LT-LS composition resulted in a significant suppression of leakage current and enhancement of polarization saturation. A remanent polarization of 16 æC/cm2 and coercive field of 20 kV/cm were measured for such thin film, which are comparable to those of hard PZT counterparts. Also, a high remanent polarization and coercive field of 30 æC/cm2 and 95 kV/cm were achieved in 350 nm BNT-BKT-BT thin films. Longitudinal (d33) and transverse (e31, f) piezoelectric coefficients of KNN-LT-LS thin films were found to be 55 pm/V and -4.5 C/m2 respectively, prepared at the optimized conditions, whereas 350 nm BNT-BKT-BT thin films exhibited an e31, f of -2.25 C/m2. The results of this study present the great potential of KNN-LT-LS and BNT-BKT-BT thin films for piezoelectric MEMS devices and provide a baseline for future investigations on lead-free piezoelectric thin films.
Author: Yu Hong Jeon
Publisher:
ISBN:
Category : Bismuth compounds
Languages : en
Pages : 189
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Book Description
Piezoelectric materials have been widely used in electromechanical actuators, sensors, and ultrasonic transducers. Among these materials, lead zirconate titanate Pb(Zr[subscript 1-x]Ti[subscript x])O3 (PZT) has been primarily investigated due to its excellent piezoelectric properties. However, environmental concerns due to the toxicity of PbO have led to investigations into alternative materials systems. Bismuth-based perovskite piezoelectric materials such as (Bi0.5, Na0.5)TiO3 - (Bi0.5K0.5)TiO3 (BNT - BKT), (Bi0.5, Na0.5)TiO3 - (Bi0.5K0.5)TiO3 - BaTiO3(BNT - BKT - BT), (Bi0.5K0.5)TiO3 - Bi(Zn0.5, Ti0.5)O3 (BKT - BZT), and (Bi0.5, Na0.5)TiO3 - (Bi0.5K0.5)TiO3 - Bi(Mg0.5, Ti0.5)O3 (BNT - BKT - BMgT) have been explored as potential alternatives to PZT. These materials systems have been extensively studied in bulk ceramic form, however many of the ultimate applications will be in thin film embodiments (i.e., microelectromechanical systems). For this reason, in this thesis these lead-free piezoelectrics are synthesized in thin film form to understand the structure-property-processing relationships and their impact on the ultimate device response. Fabrication of high quality of 0.95BKT - 0.05BZT thin films on platinized silicon substrates was attempted by pulsed laser deposition. Due to cation volatility, deposition parameters such as substrate temperature, deposition pressure, and target-substrate distance, as well as target overdoping were explored to achieve phase pure materials. This route led to high dielectric loss, indicative of poor ferroelectric behavior. This was likely a result of the poor thin film morphology observed in films deposited via this method. Subsequently, 0.8BNT - 0.2BKT, 85BNT - 10BKT - 5BT, and 72.5BNT - 22.5BKT - 5BMgT (near morphotropic phase boundary composition) were synthesized via chemical solution deposition. To compensate the loss of A-site cations, overdoped precursor solutions were prepared. Crystallization after each spin cast layer were required to produce phase pure material. Good permittivities and low dielectric loss over the frequency range of 100 Hz to 1 MHz were obtained. Dependent upon annealing conditions, various film morphologies and compositional distributions were observed via electron microscopy and composition measurements. As opposed to previously reported work, good ferroelectric response at low frequency (200 Hz) were found. For BNT - BKT - BMgT, the maximum polarization was over 50 [micro]C/cm2 with high d[subscript 33,f] of 75 pm/V were obtained. Additionally, the extrinsic and intrinsic contributions to the dielectric response for solution-derived BNT - BKT and BNT - BKT - BMgT films were studied via Rayleigh analysis. For sub-switching fields a good agreement between predicted polarization behavior from Rayleigh analysis and experimentally measured polarization indicated the validity of this approach for BNT-based thin films. Results of this thesis proved that high quality bismuth-based piezoelectric thin films with good electrical response can be fabricated with suppression of cation volatility for various processing conditions. Furthermore, these thin films can be considered as alternatives to PZT thin films as potential candidates for piezoelectric-based microelectromechanical systems (MEMS).
Author: KOJI SUGIOKA.
Publisher:
ISBN: 9783319695372
Category : Lasers in engineering
Languages : en
Pages :
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Book Description
This handbook provides a comprehensive review of the entire field of laser micro and nano processing, including not only a detailed introduction to individual laser processing techniques but also the fundamentals of laser-matter interaction and lasers, optics, equipment, diagnostics, as well as monitoring and measurement techniques for laser processing. Consisting of 11 sections, each composed of 4 to 6 chapters written by leading experts in the relevant field. Each main part of the handbook is supervised by its own part editor(s) so that high-quality content as well as completeness are assured. The book provides essential scientific and technical information to researchers and engineers already working in the field as well as students and young scientists planning to work in the area in the future. Lasers found application in materials processing practically since their invention in 1960, and are currently used widely in manufacturing. The main driving force behind this fact is that the lasers can provide unique solutions in material processing with high quality, high efficiency, high flexibility, high resolution, versatility and low environmental load. Macro-processing based on thermal process using infrared lasers such as CO2 lasers has been the mainstream in the early stages, while research and development of micro- and nano-processing are becoming increasingly more active as short wavelength and/or short pulse width lasers have been developed. In particular, recent advances in ultrafast lasers have opened up a new avenue to laser material processing due to the capabilities of ultrahigh precision micro- and nanofabrication of diverse materials. This handbook is the first book covering the basics, the state-of-the-art and important applications of the dynamic and rapidly expanding discipline of laser micro- and nanoengineering. This comprehensive source makes readers familiar with a broad spectrum of approaches to solve all relevant problems in science and technology. This handbook is the ultimate desk reference for all people working in the field.
Author: Shashank Priya
Publisher: Springer Science & Business Media
ISBN: 1441995986
Category : Technology & Engineering
Languages : en
Pages : 521
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Book Description
Ecological restrictions in many parts of the world are demanding the elimination of Pb from all consumer items. At this moment in the piezoelectric ceramics industry, there is no issue of more importance than the transition to lead-free materials. The goal of Lead-Free Piezoelectrics is to provide a comprehensive overview of the fundamentals and developments in the field of lead-free materials and products to leading researchers in the world. The text presents chapters on demonstrated applications of the lead-free materials, which will allow readers to conceptualize the present possibilities and will be useful for both students and professionals conducting research on ferroelectrics, piezoelectrics, smart materials, lead-free materials, and a variety of applications including sensors, actuators, ultrasonic transducers and energy harvesters.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 55
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Author: Jing-Feng Li
Publisher: John Wiley & Sons
ISBN: 3527345124
Category : Technology & Engineering
Languages : en
Pages : 240
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Book Description
Provides in-depth knowledge on lead-free piezoelectrics - for state-of-the-art, environmentally friendly electrical and electronic devices! Lead zirconate titanate ceramics have been market-dominating due to their excellent properties and flexibility in terms of compositional modifications. Driven by the Restriction of Hazardous Substances Directive, there is a growing concern on the toxicity of lead. Therefore, numerous research efforts were devoted to lead-free piezoelectrics from the beginning of this century. Great progress has been made in the development of high-performance lead-free piezoelectric ceramics which are already used, e.g., for power electronics applications. Lead-Free Piezoelectric Materials provides an in-depth overview of principles, material systems, and applications of lead-free piezoelectric materials. It starts with the fundamentals of piezoelectricity and lead-free piezoelectrics. Then it discusses four representative lead-free piezoelectric material systems from background introduction to crystal structures and properties. Finally, it presents several applications of lead-free piezoelectrics including piezoelectric actuators, and transducers. The challenges for promoting applications will also be discussed. Highly attractive: Lead-free piezoelectrics address the growing concerns on exclusion of hazardous substances used in electrical and electronic devices in order to protect human health and the environment Thorough overview: Covers fundamentals, different classes of materials, processing and applications Unique: discusses fundamentals and recent advancements in the field of lead-free piezoelectrics Lead-Free Piezoelectric Materials is of high interest for material scientists, electrical and chemical engineers, solid state chemists and physicists in academia and industry.
Author: Loucas Tsakalakos
Publisher:
ISBN:
Category :
Languages : en
Pages : 220
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Author: Ashley D. Mason
Publisher:
ISBN:
Category : Bismuth compounds
Languages : en
Pages : 137
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Book Description
Piezoelectric materials convert mechanical strain into a dielectric displacement, as well as the converse, allowing these materials to be used as sensors, actuators, and transducers. Currently, lead zirconate titanate (PZT) is the primary material used in these applications. Due to environmental toxicity and safety concerns associated with Pb, development of alternative materials is necessary. Bi-based systems are an attractive area of research in both bulk ceramic and thin film embodiments. Although progress in developing bismuth sodium titanate (BNT)-based solid solutions has been impressive, the combination of cation volatility and high processing temperatures for both bulk ceramic and thin film fabrication can lead to changes in stoichiometry and create defects within the system which can significantly impact material properties. One of the main sources of defects is often presumed to be related to cation volatility. As such, the diffusion behavior of volatile cations within BNT-bismuth potassium titanate (BKT)-based thin films was studied using transmission electron microscopy, electron energy loss spectroscopy, and energy dispersive x-ray spectroscopy. Both in-situ and ex-situ experiments were performed where the objectives were to: (1) observe crystallization processes in a single layer film, and (2) map the locations of Bi, Na, and K throughout the thin film, bottom electrode, and substrate cross-section. Results indicated that Bi, Na, and K had all diffused into the Pt bottom electrode, and in some cases the underlying buffer layers. In addition to the aforementioned volatilization into atmosphere, this diffusion could also impact film stoichiometry and material properties and should be accounted for. Multi-layer BNT-BKT-bismuth zinc titanate (BZnT) thin films were fabricated via chemical solution deposition. X-ray diffraction and atomic force microscopy were used to study structure and morphology changes with processing parameters. The dielectric, ferroelectric,and piezoelectric properties were characterized and values of the effective out-of-plane piezoelectric coefficient, d33,f, were extracted from double beam laser interferometry measurements. Dielectric constants and loss ranged from 380-800 and 2-8% respectively as a function of thin film composition. For 0.8 mm diameter top electrodes, the maximum value measured for effective d33,f was approximately 80 pm/V. Lastly, electrical fatigue measurements showed that while the effective d33,f was larger for compositions closer to the BNT-BKT morphotropic phase boundary (MPB), those further away were able to withstand a higher number of cycles, up to three orders of magnitude, at ± 400 kV/cm. Results from this dissertation were: (i) An increase in the number of possible end members (e.g. BZnT, BMgT, BaTiO3 (BT)) for BNT-BKT-based thin films fabricated at OSU (ii) An expansion in the range of compositions fabricated rather than commonly studied MPB compositions: while the maximum observed values for effective d33 in bulk BNT-BKTBZnT were further towards the BKT-rich side of the ternary phase diagram, the same is not true in thin films (iii) Motivation for further study of the diffusion of volatile cations in BNT-based thin film systems: cations are not only volatilized into atmosphere during high temperature processing, but can also diffuse out of the thin film into and through the bottom electrode (iv) If longer device lifetime supercedes the need for the highest obtainable piezoelectric coefficients, compositions away from the BNT-BKT MPB may be of interest.
Author: Lucymarie Mantese
Publisher:
ISBN:
Category :
Languages : en
Pages : 146
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Author: Christian Cornelius Schröter
Publisher:
ISBN:
Category :
Languages : en
Pages : 207
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Book Description
