Genshui Wang

Charge-discharge properties of lead zirconate stannate titanate ceramics

The charge-discharge properties of lanthanum- and niobium-doped lead zirconate stannate titanate ceramics were investigated by directly measuring the hysteresis loops, dielectric constants under a dc bias field, and pulse discharge current-time curves after varying charge-discharge circulations. It was found that there was no significant effect of the charge-discharge circulation on these properties. The first pulse current peak reached 1.8 kA at 40 kV/cm, and most of the stored charge was released in 500 ns. These results show that the obtained slanted ceramics with high energy density can withstand hundreds of charge-discharge circulations and are very promising for pulse capacitor applications.

Temperature-dependent stability of energy storage properties of Pb0.97La0.02(Zr0.58Sn0.335Ti0.085)O3 antiferroelectric ceramics for pulse power capacitors

The dielectric properties and electrical hysteresis behaviors of Pb0.97La0.02(Zr0.58Sn0.335Ti0.085)O3 antiferroelectric (AFE) ceramics were investigated in this work with an emphasis on energy storage properties. Three phase transition points can be detected as temperature increases. AFE and paraelectric phases are found to coexist from 100 °C to 170 °C. The room temperature recoverable energy density is 1.37 J/cm3 at 8.6 kV/mm. With increasing temperature (from 20 °C to 100 °C) and frequency (from 0.01 to 100 Hz) under 8.6 kV/mm, the variation of recoverable energy density was less than 15%, all higher than 1.2 J/cm3. All the corresponding energy efficiencies were no less than 75%. The high energy density, high energy efficiency, and their weak dependence on temperature and frequency during a wide scope indicate that these antiferroelectric ceramics are quite promising to be used for pulse power capacitors applications.

Reversible pyroelectric response in Pb0.955La0.03(Zr0.42Sn0.40Ti0.18)O3 ceramics near its phase transition

Phase transition and pyroelectric behaviors of Pb0.955La0.03(Zr0.42Sn0.40Ti0.18)O3 (PLZST) ceramics were investigated as functions of temperature and electric field. Pyroelectric coefficient about 160×10−8 C cm−2 K−1 is detected at the electric-field-induce ferroelectric (FEIN) to antiferroelectric phase transition for the poled samples. Reversible pyroelectric response with a pyroelectric coefficient maximum about 50×10−8 C cm−2 K−1 is obtained when a dc bias is applied on the depoled sample simultaneously.

Enhanced polarization switching and energy storage properties of Pb0.97La0.02(Zr0.95Ti0.05)O3 antiferroelectric thin films with LaNiO3 oxide top electrodes

Polarization switching and energy storage properties of highly (100) oriented antiferroelectric (AFE) (Pb,La)(Zr,Ti)O3 thin films (≤250 nm) deposited via a sol-gel process with both LaNiO3 and Pt top electrodes were investigated. By using LaNiO3 top electrodes, the energy density as well as energy efficiency can be enhanced by 4.6 J/cm3 and 11%, respectively. Furthermore, the films with LaNiO3 top electrodes are more capable of providing high energy density over a wide temperature regime above room temperature compared to Pt. This work clearly highlights that oxide top electrodes can greatly improve the energy storage performance of antiferroelectric thin film capacitors.

Microwave properties of epitaxial (111)-oriented Ba0.6Sr0.4TiO3 thin films on Al2O3(0001) up to 40 GHz

Perovskite Ba0.6Sr0.4TiO3 (BST) thin films have been grown on Al2O3(0001) substrates without/with inserting an ultrathin TiOx seeding layer by rf magnetron sputtering. X-ray diffraction and pole figure studies reveal that the film with the TiOx layer (12-A-thick) is highly oriented along the (111) direction and exhibits a good in-plane relationship of BST(111)∥Al2O3(0001). The high frequency dielectric measurements demonstrate that the complex permittivity (e=e′−je″) is well described by a Curie–von Scheidler dispersion with an exponent of 0.40. The resulting epitaxial BST films show high permittivity (∼428) and tunability (∼41%, at 300 kV/cm and 40 GHz) and their microwave properties (1–40 GHz) potentially could be made suitable for tunable devices.

Enhancement of energy storage in epitaxial PbZrO3 antiferroelectric films using strain engineering

We demonstrate an approach to enhance the energy storage density W of antiferroelectric film through simple altering a crystallographic orientation of the substrate. We reveal that the antiferroelectric phase stability of PbZrO3 can be enhanced for the (110) or (111) SrTiO3 substrate orientation, thus suppresses the antiferroelectric-ferroelectric phase transition to higher electric field with ∼120 kV/cm increment. In addition, the polarization values of these films are also favorably increased hence increases W by 5.3 J/cm3 at 700 kV/cm. The observed enhancement is found to originate from a high sensitivity of phase transition to mechanical confinements due to the volume expansion at the transition.

Large stable strain memory effect in poled Mn-doped Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ceramics

Large strain memory effect was confirmed in the poled and aged Mn-doped 0.05Pb(Mn1/3Sb2/3)O3-0.50PbZrO3-0.45PbTiO3 ceramics due to the presence of asymmetric strain hysteresis curve with two stable strain states at zero electric field. This strain memory is two times larger than that of the unipolar strain output. Moreover, the large strain memory effect is quite stable at high electric field or down to 0.01 Hz and shows good stability even after 20 000 fatigue cycles. These results indicate that strain memory piezoelectric actuator, which could keep its output strain without any operating fields, may be fabricated using this kind of material.

Enhanced pyroelectric properties of Cax(Sr0.5Ba0.5)1−xNb2O6 lead-free ceramics

Cax(Sr0.5Ba0.5)1−xNb2O6 [CSBN(x), x = 0.00, 0.10, 0.15, and 0.20] lead-Free ceramics were prepared by a traditional solid-state reaction technique. Dielectric, ferroelectric, and pyroelectric properties of CSBN(x) lead-Free ceramics were systematically investigated. The pyroelectric properties of CSBN(x) have been enhanced remarkably due to Ca addition and reached the maximum values at x = 0.15, with pyroelectric coefficient of 3.61 × 10−8 C/cm2 K and pyroelectric figure of merit of Fi = 172 pm/V, Fv = 0.021 m2/C, and Fd = 11.5 μPa−1/2, which are superior to other lead-free ferroelectric ceramics. These results indicate the potential of CSBN(x) ceramics for infrared detector applications.

Optical properties of Bi3.25La0.75Ti3O12 thin films using spectroscopic ellipsometry

Using spectroscopic ellipsometry, the optical properties of the Bi3.25La0.75Ti3O12 (BLT) thin films with different film thicknesses on platinized silicon substrates prepared by chemical solution methods have been investigated in the 400–1700 nm wavelength range. By fitting the measured ellipsometric parameter (Ψ and Δ) data with a multilayer model system and the classical dispersion relation for the BLT thin films, the optical constants and thicknesses of the thin films have been obtained. Meanwhile, some degree of inhomogeneity (in the form of low density layers or surface roughness) has been found in the BLT thin films except for the thinnest film, which was homogeneous throughout its thickness. The multilayer model system became very complicated with increasing thickness. It indicated that the microstructure of the BLT thin films varied with increasing thickness. The refractive index n of the BLT thin films increases with increasing thickness, and on the contrary, the extinction coefficient k decreases...

High charge-discharge performance of Pb0.98La0.02(Zr0.35Sn0.55Ti0.10)0.995O3 antiferroelectric ceramics

The energy storage performance and charge-discharge properties of Pb0.98La0.02(Zr0.35Sn0.55Ti0.10)0.995O3 (PLZST) antiferroelectric ceramics were investigated through directly measuring the hysteresis loops and pulse discharge current-time curves. The energy density only varies 0.2% per degree from 25 °C to 85 °C, and the energy efficiency maintains at about 90%. Furthermore, an approximate calculating model of maximum power density pmax was established for the discharge process. Under a relatively high working electric field (8.2 kV/mm), this ceramics possess a greatly enhanced power density of 18 MW/cm3. Moreover, the pulse power properties did not show degradation until 1500 times of charge-discharge cycling. The large released energy density, high energy efficiency, good temperature stability, greatly enhanced power density, and excellent fatigue endurance combined together make this PLZST ceramics an ideal candidate for pulse power applications.