Aging effect evolution during ferroelectric-ferroelectric phase transition: A mechanism study

Aging can significantly modify the dielectric, piezoelectric, and ferroelectric performance of ferroelectrics. However, little attention has been paid to the aging effect during ferroelectric-ferroelectric phase transitions that is essentially correlated with real applications. In this letter, the authors report the aging effect evolution between two ferroelectric phases in an acceptor-doped piezoceramics. The results show that aging-induced double hysteresis loops were exhibited in different ferroelectric phases, but disappeared during ferroelectric-ferroelectric phase transitions, suggesting the mechanism that the intrinsic restoring force for the reversible switching of domains caused by the alignment of defect dipoles was weakened due to ferroelectric dipole reorientation

Large electrocaloric effect in highly (001)-oriented 0.67PbMg 1/3Nb2/3O3-0.33PbTiO3 thin films

(001)-oriented 0.67PbMg1/3Nb2/3O3–0.33PbTiO3 thin films with a pure perovskite crystalline phase were deposited on LaNiO3-coated SiO2/Si substrates by the rf magnetron sputtering technique. We found that the as-grown thin films with (001)-oriented texture possess not only excellent dielectric and ferroelectric properties but also a large electrocaloric effect (14.5 K in 12 V, i.e., 1.21 K/V) which is attributed to the large polarization and entropy change during the ferroelectric–paraelectric phase transition at a high electric field. The discovery of the large electrocaloric effect in highly textured ferroelectric thin films widens their potential applications, such as in solid-state electrical refrigeration

Large electrocaloric effect of highly (100)-oriented 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 thin films with a Pb(Zr0.3Ti0.7)O3/PbOx buffer layer

0.68PbMg1/3Nb2/3O3–0.32PbTiO3 (PMN–PT) thin films with a lead zirconate titanate Pb(Zr0.3Ti0.7)O3 (PZT)/PbOx buffer layer were deposited on Pt/TiO2/SiO2/Si substrates by radio frequency magnetron sputtering technique, and pure perovskite crystalline phase with highly (100)-preferred orientation was formed in the ferroelectric films. We found that the highly (100)-oriented thin films possess not only excellent dielectric and ferroelectric properties but also a large electrocaloric effect (13.4 K at 15 V, i.e., 0.89 K/V) which is attributed to the large electric field-induced polarization and entropy change during the ferroelectric–paraelectric phase transition. The experimental results indicate that the use of PZT/PbOx buffer layer can induce the crystal orientation and phase purity of the PMN–PT thin films, and consequently enhance their electrical properties

Unveiling the Effect of Surface and Bulk Structure on Electrochemical Properties of Disproportionated SiOx Anodes

As a promising lithium-ion battery anode materials, silicon suboxides (SiOx) exhibit elusive microstructure with atomic-scale disproportionation which reveals a strong relation to performance. Generally, the structure of SiOx could be tuned via high-temperature treatment. In this work, disproportionated SiOx are prepared to systematically discuss the internal relationship among microstructure, physicochemical properties and electrochemical performance. After annealing, amorphous SiO2 and nanocrystalline Si appear, and the SiO2 accumulating on the surface results in large resistance and low Li-ion diffusivity, which leads to large overpotential and poor performance. If mechanical milling is employed followed by annealing, the SiO2 layer can be crushed, SiOx and Si with electrochemical activity are uncovered. Further research on the SiOx with diverse degrees of disproportionation indicates that proper amount of Si and SiO2 determines the optimal electrochemical performance. This result gives an in-depth understanding and probable guidance to the modification investigation of SiOx anode for Li-ion batteries

Large piezoelectric effect in lead-free Ba(Zr0.2Ti 0.8)O3-(Ba0.7Ca0.3)TiO3 films prepared by screen printing with solution infiltration process

High-quality piezoelectric Ba(Zr0.2Ti0.8)O3–50(Ba0.7Ca0.3)TiO3 films with very dense and homogenous microstructure were fabricated using chemical solution infiltration into porous screen-printed films. The films with a thickness of 10 μm exhibited high relative permittivity of 2380, low dielectric loss of 1.6% (at 10 kHz), large remanent polarization of 22 μC/cm2, and large longitudinal piezoelectric constant d33 of 220 pC/N, which is even better than the case of lead-based piezoelectric films. The excellent electrical propertiesmake the films a promising candidate for practical applications in lead-free microdevices such as piezoelectric microelectromechanical systems

Large piezoelectric effect in low-temperature-sintered lead-free (ba0.85ca0.15)(zr0.1ti0.9)o-3 thick films

High-quality piezoelectric (Ba0.85Ca0.15)(Zr0.1Ti0.9)O-3 thick films with dense and homogenous microstructures were fabricated at a low sintering temperature (900 degrees C) using a CuBi2O4 sintering aid. The 10 mu m thick film exhibited a high longitudinal piezoelectric constant d(33,eff) of 210 pC/N with estimated unconstrained d(33) value of 560 pC/N very close to that in the corresponding bulks. Such excellent piezoelectric effect in the low-temperature sintered (Ba0.85Ca0.15)(Zr0.1Ti0.9)O-3 thick films is comparable to the case of lead-based PZT thick films, and may be a promising application in lead-free microdevices such as piezoelectric microelectromechanical systems (MEMS)

Reliable laser fabrication : the quest for responsive biomaterials surface

Laser techniques have been traditionally used for material processing. Currently, there is growing recognition that lasers are a reliable fabrication tool that can be used to tailor the surfaces of biomaterials for tissue-engineering applications. Herein, we review the use of selected lasers with a wide range of wavelengths and pulses. We present typical examples to illustrate the basic fabrication principles and significance of laser fabrication in tailoring biomaterial surfaces with different geometric features. We also discuss the tissue-engineering applications of laser-fabricated biomaterials; these biomaterial surfaces show promise in delivering physicochemical cues for hard and soft tissue reconstruction

Enhanced piezoelectric properties of solution-modified Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 thick films

High-quality piezoelectric 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 thick films with the thickness of 6 μm were prepared by screen printing with solution infiltration process. The modified films near the morphotropic phase boundary (MPB) showed very dense and homogenous microstructure with large grain size, and presented markedly enhanced piezoelectric properties with large remanent polarization of 22 μC/cm2 and a longitudinal piezoelectric constant d33 of 220 pC/N, which were over two times higher than those of the screen printed films without the solution infiltration process. The excellent piezoelectric properties comparable to the case of lead-based thick films, make the modified films a promising candidate for practical applications in lead-free microdevices such as piezoelectric microelectromechanical systems (MEMS)

High dielectric tunability of Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 thick films modified by a solution-immersion process

High-quality lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 thick films with the thickness of 8 μm were prepared by screen printing with a solution-immersion process. The solution-modified films near the morphotropic phase boundary (MPB) showed very dense and homogenous microstructure with large grain size, and exhibited moderate dielectric constant of 1680 and low dielectric loss of 1.38% at 10 kHz with 0 V bias at room temperature. High dielectric tunability up to 76.7% at 12 kV/mm and 10 kHz was achieved in the modified films. The excellent dielectric properties associated with good microstructure and MPB composition, make the lead-free films be a promising candidate for dielectric tunable capacitor applications