A. R. James

Bio: A. R. James is an academic researcher from Defence Metallurgical Research Laboratory. The author has contributed to research in topics: Dielectric & Ferroelectricity. The author has an hindex of 24, co-authored 89 publications receiving 1673 citations. Previous affiliations of A. R. James include Indian Institute of Science & Solid State Physics Laboratory.

Effect of poling process on piezoelectric properties of sol–gel derived BZT–BCT ceramics

Abstract: Lead free piezoelectric ceramics barium zirconate titanate-barium calcium titanate, [xBZT-(1-x)BCT] (0.48≤ x ≤0.52), were synthesized by sol-gel method. Calcination of the as-synthesized precursor powders resulted in crystalline powders with single-phase perovskite structure at 700°C, which is significantly lower than that obtained by solid-state reaction. Solid-state sintering at 1450°C resulted in highly dense microstructure with ≥95% of the theoretical density. The effect of electric poling on the piezoelectric properties of the sintered [xBZT-(1-x)BCT] ceramics is studied with varying poling temperatures and poling fields. The results indicated that optimized poling conditions are required in enhancing the piezoelectric properties of [xBZT-(1-x)BCT] ceramics. The morphotropic phase boundary (MPB) composition, 0.5BZT-0.5BCT, showed a high remanent polarization (P r) of 12.2μC/cm2 and a low coercive field (E c) of ~0.14kV/mm. The optimized poling conditions resulted in high piezoelectric charge coefficient d 33 ~637pC/N, large electromechanical coupling coefficient k p ~59.6%, a large strain of 0.157%, a large piezoelectric voltage constant g 33 ~29mVm/N for (0.5BZT-0.5BCT) composition. In this report, the excellent piezoelectric properties of the sol-gel derived BZT-BCT ceramics has been analysed and correlated to its structure and poling conditions.

Structural, ferroelectric and optical properties of PZT thin films

Abstract: We report on the structural, ferroelectric and optical properties of lead zirconate titanate (PZT) thin films (with a molar ratio of Zr:Ti::65:35) deposited by sol–gel technique on ITO-coated corning 7059 glass substrates. A seed layer of PbTiO3 (0.1mm) was coated by sol–gel on the substrates before depositing PZT. A metal/ferroelectric/metal (MFM) structure was used for electrical property measurements, formed by depositing gold electrodes on top of the film. The films were characterized for C–V, I–V, P–E and optical transmission. Relatively low remnant polarization (Pr ¼ 3:6mC=cm 2 ) was observed for the films. Value of optical band gap was found to be 3.4 eV. The results are discussed.

BaTiO3-based piezoelectrics: Fundamentals, current status, and perspectives

Abstract: We present a critical review that encompasses the fundamentals and state-of-the-art knowledge of barium titanate-based piezoelectrics. First, the essential crystallography, thermodynamic relations, and concepts necessary to understand piezoelectricity and ferroelectricity in barium titanate are discussed. Strategies to optimize piezoelectric properties through microstructure control and chemical modification are also introduced. Thereafter, we systematically review the synthesis, microstructure, and phase diagrams of barium titanate-based piezoelectrics and provide a detailed compilation of their functional and mechanical properties. The most salient materials treated include the (Ba,Ca)(Zr,Ti)O3, (Ba,Ca)(Sn,Ti)O3, and (Ba,Ca)(Hf,Ti)O3 solid solution systems. The technological relevance of barium titanate-based piezoelectrics is also discussed and some potential market indicators are outlined. Finally, perspectives on productive lines of future research and promising areas for the applications of these ma...

Piezoelectric MEMS sensors: state-of-the-art and perspectives

Abstract: Over the past two decades, several advances have been made in micromachined sensors and actuators. As the field of microelectromechanical systems (MEMS) has advanced, a clear need for the integration of materials other than silicon and its compounds into micromachined transducers has emerged. Piezoelectric materials are high energy density materials that scale very favorably upon miniaturization and that has led to an ever-growing interest in piezoelectric films for MEMS applications. At this time, piezoelectric aluminum-nitride-based film bulk acoustic resonators (FBAR) have already been successfully commercialized. Future innovations and improvements in inertial sensors for navigation, high-frequency crystal oscillators and filters for wireless applications, microactuators for RF applications, chip-scale chemical analysis systems and countless other applications hinge upon the successful miniaturization of components and integration of piezoelectrics and metals into these systems. In this article, a comprehensive review of micromachined piezoelectric transducer technology will be presented. Piezoelectric materials in bulk and thin film forms will be reviewed and fabrication techniques for the integration of these materials for microsensor applications will be presented. Recent advances in various piezoelectric microsensors will be presented through specific examples. This review will conclude with a critical assessment of the future trends and promise of this technology.