Lead-Free Piezoceramics Research Papers - Academia.edu (original) (raw)

Book Description This monograph covers the fundamentals, fabrication, testing, and modeling of ambient energy harvesters based on three main streams of energy-harvesting mechanisms: piezoelectrics, ferroelectrics, and pyroelectrics. It... more

Book Description This monograph covers the fundamentals, fabrication, testing, and modeling of ambient energy harvesters based on three main streams of energy-harvesting mechanisms: piezoelectrics, ferroelectrics, and pyroelectrics. It addresses their commercial and biomedical applications, as well as the latest research results. Graduate students, scientists, engineers, researchers, and those new to the field will find this book a handy and crucial reference because it provides a comprehensive perspective on the basic concepts and recent developments in this rapidly expanding field.

Barium titanate–nickel composites (BaTiO3–Ni) were synthesized at a low temperature using a sol–gel method and sintered in a reducing atmosphere. XRD,FE-SEM,Raman spectroscopy and TGA were performed to confirm the phases of BaTiO3 and... more

Barium titanate–nickel composites (BaTiO3–Ni) were synthesized at a low temperature using a sol–gel method and sintered in a reducing atmosphere. XRD,FE-SEM,Raman spectroscopy and TGA were performed to confirm the phases of BaTiO3 and Ni,themorphology and tetragonal crystal structure of BaTiO3 and the weight loss.The results indicate that by controlling the experimental conditions (temperature and atmosphere) during the sintering process, the grain size of the BaTiO3–Ni composite can be controlled.The average grain size of the dense BaTiO3–Ni composite was in the range of 0.6–1.5 mm. In addition,the dielectric constant increased from 2000 for monolithic BaTiO3 to
11,000 by increasing the Ni content.The enhanced dielectric properties of the BaTiO3–Ni composite are due to the well-dispersed nickel particles in the BaTiO3 matrix.

Ceramics in the system (Bi0.5K0.5)TiO3-BiFeO3 have good electromechanical properties and temperature stability. However, the high conductivity inherent in BiFeO3-based ceramics complicates measurement of the ferroelectric properties. In... more

Ceramics in the system (Bi0.5K0.5)TiO3-BiFeO3 have good electromechanical properties and temperature stability. However, the high conductivity inherent in BiFeO3-based ceramics complicates measurement of the ferroelectric properties. In the present work, doping with niobium
(Nb) is carried out to reduce the conductivity of (Bi0.5K0.5)TiO3-BiFeO3. Powders of composition 0.4(K0.5Bi0.5)Ti1xNbxO3-0.6BiFe1xNbxO3 (x = 0, 0.01 and 0.03) are prepared by the mixed oxide method and sintered at 1050 C for 1 h. The effect of Nb doping on the structure is examined by X-ray diffraction. The microstructure is examined by scanning electron icroscopy. The variation in relative permittivity with temperature is measured using an impedance analyzer. Ferroelectric properties are measured at room temperature using a Sawyer Tower circuit. Piezoelectric properties are measured using a d33 meter and a contact type displacement sensor. All the samples have high density, a rhombohedral unit cell and equiaxed, micron-sized grains. All the samples show
relaxor-like behavior. Nb doping causes a reduction in conductivity by one to two orders of magnitude at 200 C. The samples have narrow P-E loops reminiscent of a linear dielectric. The samples all possess bipolar butterfly S-E loops characteristic of a classic ferroelectric material. Nb doping causes a decrease in d33 and Smax/Emax.

Improvement of dielectric properties of commonly used electroceramic materials plays an important role in the development of modern electronics. This paper has described the preparations and properties of lead-free BaTiO 3-based ceramics... more

Improvement of dielectric properties of commonly used electroceramic materials plays an important role in the development of modern electronics. This paper has described the preparations and properties of lead-free BaTiO 3-based ceramics obtained from mechanochemically synthesized powder. Ba 1−x Ca x TiO 3 powders with different calcium contents (0 x 0.20) have been successfully obtained by mechanochemical synthesis directly at room temperature (without any additional thermal treatment). Mechanochemically triggered reaction, leading to the formation of perovskite phase, has been monitored by XRD at different stages. Pure and Ca-doped barium titanate powders have been consolidated (1) by pressing and subsequently conventional sintering or (2) by hot pressing. The influence of the sintering method on the dielectric properties of the ceramics has been investigated by dielectric spectroscopy in the temperature range from 25 to 180 °C. Both the sintering method and the doping with Ca have a strong effect on the dielectric permittivity and dielectric losses of barium titanate ceramics.

Coupling of order parameters provides a means to tune functionality in advanced materials including multiferroics, superconductors, and ionic conductors. We demonstrate that the response of a frustrated ferroelectric state leads to... more

Coupling of order parameters provides a means to tune functionality in advanced materials including multiferroics, superconductors, and ionic conductors. We demonstrate that the response of a frustrated ferroelectric state leads to coupling between order parameters under electric field depending on grain orientation. The strain of grains oriented along a specific crystallographic direction, 〈h00〉, is caused by converse piezoelectricity originating from a ferrodistortive tetragonal phase. For 〈hhh〉 oriented grains, the strain results from converse piezoelectricity and rotostriction, as indicated by an antiferrodistortive instability that promotes octahedral tilting in a rhombohedral phase. Both strain mechanisms combined lead to a colossal local strain of (2.4 ± 0.1) % and indicate coupling between oxygen octahedral tilting and polarization, here termed " rotopolarization ". These findings were confirmed with electromechanical experiments, in situ neutron diffraction, and in situ transmission electron microscopy in 0.75Bi 1/2 Na 1/2 TiO 3-0.25SrTiO 3. This work demonstrates that polar and non-polar instabilities can cooperate to provide colossal functional responses.

ABSTRACT Barium titanate-nickel composites (BaTiO3-Ni) were synthesized at a low temperature using a sol gel method and sintered in a reducing atmosphere. XRD, FE-SEM, Raman spectroscopy and TGA were performed to confirm the phases of... more

ABSTRACT Barium titanate-nickel composites (BaTiO3-Ni) were synthesized at a low temperature using a sol gel method and sintered in a reducing atmosphere. XRD, FE-SEM, Raman spectroscopy and TGA were performed to confirm the phases of BaTiO3 and Ni, the morphology and tetragonal crystal structure of BaTiO3 and the weight loss. The results indicate that by controlling the experimental conditions (temperature and atmosphere) during the sintering process, the grain size of the BaTiO3-Ni composite can be controlled. The average grain size of the dense BaTiO3-Ni composite was in the range of 0.6-1.5 mu m. In addition, the dielectric constant increased from similar to 2000 for monolithic BaTiO3 to similar to 11,000 by increasing the Ni content. The enhanced dielectric properties of the BaTiO3-Ni composite are due to the well-dispersed nickel particles in the BaTiO3 matrix. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.