Environment-friendly lead-free piezoelectric ceramics have been studied extensively in the past decade with great progress particularly in systems based on a niobate perovskite compound formulated as (K, Na)NbO3 (abbreviated as KNN). A comprehensive review on the latest development of KNN-based piezoelectric ceramics is presented in this article, including the phase structure, property enhancement approaches, and sintering processes as well as the status of some promising applications. The phase structure of KNN was reexamined and associated with the effect of chemical modification on its tetragonal-to-orthorhombic transition. Then, a special focus is placed on the temperature dependence of piezoelectric properties of KNN-based ceramics, followed by reviewing the recent approaches devoted to the temperature-stability enhancement. The processing fundamentals related to the sintering of KNN-based ceramics are also presented with an emphasis on compositional and microstructural control. Finally, this review introduces several industrial attempts of traditional piezoceramic products using KNN-based ceramics and the studies on some promising application in authors' laboratory.

(K, Na)NbO3-Based Lead-Free Piezoceramics: Fundamental Aspects, Processing Technologies, and Remaining Challenges

Systems and methods are described for obtaining and acting upon information indicative of circulatory health and related phenomena in human beings or other subjects.

Circulatory monitoring systems and methods

Smart materials, which exhibit piezoelectricity, find an eclectic range of applications in the industry. The direct piezoelectric effect has been widely used in sensor design, and the inverse piezoelectric effect has been applied in actuator design. Ever since 1954, PZT and BaTiO3 were widely used for sensor and actuator applications despite their toxicity, brittleness, inflexibility, etc. With the discovery of PVDF in 1969, followed by development of copolymers, a flexible, easy to process, nontoxic, high density alternate with high piezoelectric voltage coefficient was available. In the past 20 years, heterostructural materials like polymer ceramic composites, have received lot of attention, since these materials combine the excellent pyroelectric and piezoelectric properties of ceramics with the flexibility, processing facility, and strength of the polymers resulting in relatively high dielectric permittivity and breakdown strength, which are not attainable in a single phase piezoelectric material. The current review article is an attempt to provide a compendium of all the work carried out with reference to PVDF-PZT composites. The review article evaluates the effect of grain size, content and other factors under the purview of dielectric and piezoelectric properties while evaluating the sensitivity of the material for sensor application. POLYM. ENG. SCI., 55:1589–1616, 2015. © 2015 Society of Plastics Engineers

Dielectric and piezoelectric properties of PVDF/PZT composites: A review

In the last 25 years, piezoelectric ceramic-polymer composites have been conceptualized, prototyped, fabricated, and implemented in an array of applications encompassing medical imaging and military missions, among others. A detailed snapshot of the materials used, and a detailed account of the major innovative methods developed in making various piezoelectric ceramic-polymer composites are presented. The salient aspects of processing of such composites are summarized, and structure-processing-property relations are described using connectivity as the unifying central concept. Computer-aided design (CAD)-based fabrication methods, which result in composites whose structural complexity surpass that of composites obtained with traditional methods, are described to introduce the reader to novel concepts in processing of piezocomposites. A brief survey of some recent advances made in modeling of (0-3), (1-3), and (2-2) composites also is provided.

Piezoelectric composites for sensor and actuator applications

Combining a piezoelectric ceramic and a passive polymer to form a piezocomposite allows the transducer engineer to design new piezoelectrics that offer substantial advantages over the conventional piezoelectric ceramics and polymers. The rod composite geometry provides materials with enhanced electromechanical coupling and with acoustic impedance close to that of tissue; these factors yield transducers for medical ultrasonic imaging with high sensitivity and compact impulse response. The dice-and-fill technique produces piezocomposites that can be readily formed into complex shapes to facilitate focusing the ultrasonic beam. Proper design of the rod spacing yields materials that exhibit low crosstalk between array elements formed by patterning the electrode alone, without cutting between the elements. In this way, curved annular arrays have been made that provide high-quality clinical images of substantial diagnostic value to physicians. Included is an extensive bibliography of papers documenting the role of piezocomposites in ultrasonic imaging transducers. >

The role of piezocomposites in ultrasonic transducers

The etching of ceramic PbTi1−xZrxO3 (PZT) by XeCl excimer laser radiation has been investigated. In air, the threshold fluence for etching was about 2 J/cm2. At fluences of 10 J/cm2, etch rates of 0.1 μm/pulse were observed. The geometry of etched structures can readily be defined by choosing suitable experimental conditions, suggesting potential applications of this process to the production of devices.

Excimer‐laser‐induced etching of ceramic PbTi1−xZrxO3

Selectively shaped silicon crystal bodies, such as plate- or tape-shaped bodies, having crystalline pillar-like structures therein are produced by forming a slurry from an admixture of relatively fine sized silicon particles and a liquid binder, extruding such slurry as a relatively thin layer onto a first support member, drying such extruded layer until it becomes self-supporting and removing such support member, and then sintering such dried layer in a protective gas atmosphere at temperatures below about 1430° C. until a layer of crystalline silicon particles are generated or grown having an average diameter substantially corresponding to the thickness of the dried slurry layer.

Method of producing plate- or tape-shaped silicon crystal bodies having crystalline pillar-like structures therein, equivalent to _crystalline columnar structures, for large surface solar cells

Catalytic material for reducing nitrous oxides in flue gases in the presence of ammonia in which titanium oxide is used as the starting material and the latter is milled together with vanadium oxide and one or more oxides of the elements tungsten, molybdenum, phosphorus, chromium, copper, iron, uranium and is thereafter subjected to at least one thermal treatment. Tungsten and molybdenum are substituted here entirely or partially by phosphorus in the form of its oxides or phosphates.

Process utilizing catalytic material for the reduction of nitrous oxides

The laser-induced etching of ceramic PbTi1−xZrxO3 in a hydrogen atmosphere and in air has been investigated. Visible Ar+ and Kr+ laser radiation was employed in most of the experiments. In H2 atmosphere, regular patterning of the ceramic is possible. Average etch rates reach up to about 250 μm/s.

Laser-induced chemical etching of ceramic PbTi 1−x Zr x O 3

A piezo electric motor having a reciprocating mechanical output driven by a bank of piezo ceramic bending strips, one end of each bending strip being secured in a stationary bed and the other end of each bending strip being connected to a driven member which is reciprocated by the repeated flexing of the bending strips.

Piezo electric motor

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