A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

Perspective on the Development of Lead-free Piezoceramics

After twenty years of partly quiet and ten years of partly enthusiastic research into lead-free piezoceramics there are now clear prospects for transfer into applications in some areas. This mimics prior research into eliminating lead from other technologies that resulted in restricted lead use in batteries and dwindling use in other applications. A figure of merit analysis for key devices is presented and used to contrast lead-containing and lead-free piezoceramics. A number of existing applications emerge, where the usage of lead-free piezoceramics may be envisaged in the near future. A sufficient transition period to ensure reliability, however, is required. The use of lead-free piezoceramics for demanding applications with high reliability, displacements and frequency as well as a wide temperature range appears to remain in the distant future. New devices are outlined, where the figure of merit suggests skipping lead-containing piezoceramics altogether. Suggestions for the next pertinent research requirements are provided.

Transferring lead-free piezoelectric ceramics into application

The use of unmanned aerial vehicles (UAVs) is growing rapidly across many civil application domains, including real-time monitoring, providing wireless coverage, remote sensing, search and rescue, delivery of goods, security and surveillance, precision agriculture, and civil infrastructure inspection. Smart UAVs are the next big revolution in the UAV technology promising to provide new opportunities in different applications, especially in civil infrastructure in terms of reduced risks and lower cost. Civil infrastructure is expected to dominate more than $45 Billion market value of UAV usage. In this paper, we present UAV civil applications and their challenges. We also discuss the current research trends and provide future insights for potential UAV uses. Furthermore, we present the key challenges for UAV civil applications, including charging challenges, collision avoidance and swarming challenges, and networking and security-related challenges. Based on our review of the recent literature, we discuss open research challenges and draw high-level insights on how these challenges might be approached.

Unmanned Aerial Vehicles: A Survey on Civil Applications and Key Research Challenges

Recent development in lead-free perovskite piezoelectric bulk materials

Over the past few years, the application of camera-equipped Unmanned Aerial Vehicles (UAVs) for visually monitoring construction and operation of buildings, bridges, and other types of civil infrastructure systems has exponentially grown. These platforms can frequently survey construction sites, monitor work-in-progress, create documents for safety, and inspect existing structures, particularly for hard-to-reach areas. The purpose of this paper is to provide a concise review of the most recent methods that streamline collection, analysis, visualization, and communication of the visual data captured from these platforms, with and without using Building Information Models (BIM) as a priori information. Specifically, the most relevant works from Civil Engineering, Computer Vision, and Robotics communities are presented and compared in terms of their potential to lead to automatic construction monitoring and civil infrastructure condition assessment.

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Visual monitoring of civil infrastructure systems via camera-equipped Unmanned Aerial Vehicles (UAVs): a review of related works

Civil engineers always face the challenge of uncertainty in planning, building, and maintaining infrastructure. These works rely heavily on a variety of surveying and monitoring techniques. Unmanned aerial vehicles (UAVs) are an effective approach to obtain information from an additional view, and potentially bring significant benefits to civil engineering. This paper gives an overview of the state of UAV developments and their possible applications in civil engineering. The paper begins with an introduction to
UAV hardware, software, and control methodologies. It also reviews the latest developments in technologies
related to UAVs, such as control theories, navigation methods, and image processing. Finally, the paper
concludes with a summary of the potential applications of UAV to seismic risk assessment, transportation,
disaster response, construction management, surveying and mapping, and flood monitoring and assessment.

A review of rotorcraft Unmanned Aerial Vehicle (UAV) developments and applications in civil engineering

Water-induced degradation in lead zirconate titanate (PZT) piezoelectric ceramics was studied by a comparison experiment. In one treatment, PZT rings were immersed in a 0.01 M NaOH solution for long periods of time; in the other treatment, PZT rings were placed in a 0.01 M NaOH solution and hydrogen was evolved onto their silver electrodes by the electrolysis of water. No degradation occurred to samples immersed in the NaOH solution; but for the samples that were also treated by electrolysis of water, serious degradation occurred as their mechanical quality factor decreased dramatically and their dielectric loss increased considerably. I–V measurement showed that the resistance decreased greatly in the degraded samples, which could be explained by the formation of charge carriers due to the reduction reaction of atomic hydrogen from the electrolysis of water. It was proposed that the reduction reaction of atomic hydrogen at ambient temperature is an important origin for the degradation of piezoelectric ce...

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Water-induced degradation in lead zirconate titanate piezoelectric ceramics

TiO2-nonstoichiometry dependence on piezoelectric properties and depolarization temperature of (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

This paper presents intermetallic compound formation at the interface between the Sn/Pb solder and the PBGA metallization (Au/Ni/Cu) substrate during a first laser reflow followed by a second infrared reflow processes A thin layer of AuSn4 was observed at the interface of solder joints, its morphology was strongly dependent on the laser reflow power and heating time applied The AuSn4 compound formed at the solder joint in the first laser reflow process also changed after the secondary infrared reflow process To elucidate intermetallic formation mechanism at the interface, a finite element modeling (FEM) model is proposed, the simulated temperature profiles within the solder ball and at the solder-paid interface during laser heating are presented In addition, the shear strength of the solder joints was tested, the correlation between the shear strength and their corresponding interfacial microstructure on the solder joints are also discussed # 2002 Elsevier Science BV All rights reserved

P.C.K. Liu

Papers

A review of rotorcraft Unmanned Aerial Vehicle (UAV) developments and applications in civil engineering

Water-induced degradation in lead zirconate titanate piezoelectric ceramics

TiO2-nonstoichiometry dependence on piezoelectric properties and depolarization temperature of (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

Intermetallic compounds formation at interface between PBGA solder ball and Au/Ni/Cu/BT PCB substrate after laser reflow processes

Bismuth sodium titanate based lead-free ultrasonic transducer for microelectronics wirebonding applications