Phase transition behavior, dielectric and ferroelectric properties of (1 − x)(Bi0.5Na0.5)TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 ceramics

(1 − x)(Bi0.5Na0.5)TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 ceramics were prepared by solid state route and their phase structure and electric properties were investigated with the focus on optimizing properties for capacitor applications. There are two obvious maxima in the permittivity curves for x = 0.1–0.4 compositions. The first anomaly is suggested to be due to thermal evolution of LT-PNRs and the second one is attributed to the phase transition between the two types PNRs and the thermal evolution of HT-PNRs. The x = 0.3 sample has an operational temperature range from 87 ◦C to 310 ◦C. Most of the samples exhibit a dielectric thermal hysteresis. The x = 0.2–0.4 compositions exhibit a significant pinched P-E hysteresis loops. A large d33* of 427 pm/V was observed in 0.7BNT-0.3BCTZ composition. The x = 0.5–0.6 samples show a slim P-E hysteresis loop, and the sample with x = 0.5 exhibits high energy density of 0.6649 J/cm3 and energy storage efficiency of 83.17%, making it most suitable for application as high energy density capacitors

Research Progress in the Application of Chinese Herbal Medicines in Aquaculture: A Review

Due to increasing safety concerns regarding human consumption of fish products, an increasing number of medicinal chemicals are prohibited from use in aquaculture. As a result, Chinese herbal medicines are being increasingly used, coining the use of the term “green medicine.” Research shows that Chinese herbal medicines have many beneficial effects on fish, including growth promotion, enhancement of disease resistance, and improvement in meat quality. Many effective ingredients have been discovered in Chinese herbal medicines, which function to promote feed intake, improve meat flavor, and increase digestive enzyme activity. They also regulate and participate in processes that improve the specific and non-specific immunity of fish; however, the composition of Chinese herbal medicines is very complex and it is often difficult to identify the effective ingredients. This article reviews the latest research and application progress in Chinese herbal medicines regarding growth and feed utilization, immunity and disease resistance, and the meat quality of cultured fish. It also discusses research on the chemical constituents of classical Chinese medicinal herbs and problems with the application of Chinese herbal medicines in fish culture. This article concludes by proposing that future studies on Chinese herbal medicines should focus on how to cheaply refine and extract the effective ingredients in classical Chinese medicinal herbs, as well as how to use them efficiently in aquaculture

Impact of mechanical stress on barium titanate-based positive temperature coefficient resistive material

The sensitivity toward mechanical stress of barium titanate-based positive temperature coefficient resistor material was investigated by determining the resistance change with application of uniaxial stress from room temperature to 200 °C, which is well above the Curie temperature TC. Using the Landau–Ginsburg–Devonshire theory the resistance increases in the paraelectric state, the negligible impact of stress close to TC and the observed increase in TC with increasing stress could be rationalized. For the ferroelectric state, the stressrelated resistance increase was attributed to ferroelasticity, a change in bulk permittivity and interfacial stress inducing a piezoelectric potential. The obtained results are also discussed with respect to recent endeavors to tune properties of potential barriers in piezoelectric semiconductors by mechanical stress

Decreasing polar-structure size : achieving superior energy storage properties and temperature stability in Na0.5Bi0.5TiO3-based ceramics for low electric field and high-temperature applications

It is a grand challenge to achieve high energy density (W) and efficiency (η) simultaneously under a low electric field (LE) to obtain new high energy storage capacitors. Similar to anti-ferroelectrics, the (1-x)NBT-xBaMg1/3Nb2/3O3 relaxor material exhibits a non-linear dependence on electric field, which is caused by a reversible field-induced phase transition. This leads to high W (2.37 J/cm3) and η (81.5 %) under a LE of 155 kV/cm, which makes it superior to other bulk ceramics. Combining large polarizability of Ba2+ in A-site and local structural heterogeneity on the B-site by Mg1/3Nb2/34+, enhanced relaxor behavior and decreased polar-structure size were induced in (1-x)NBT-xBaMg1/3Nb2/3O3 ceramics. The permittivity, nevertheless, stays high at ∼2273±15 %. Furthermore, the electrical properties become stable in a wide temperature range from 44−396 °C for the sample with x=0.15. In addition, high current density/CD (450 A/cm2), power density/PD (23 MW/cm3) and discharge density/WD (0.57 J/cm3) were realized tested with pulse discharge testing. Our work will provide a development guidance for dielectric energy storage ceramics at low field and high fields with excellent temperature stability

Pulse discharge characterization of perovskite dielectric ceramics

The pulse discharge characterization of perovskite dielectric ceramics, which has confronted a barrier between research and application, has the problems of inconsistent test standards and lack of comparability. To mitigate this issue and further advance the application process, we suggest an extrinsic standard (for convenience of comparison) for energy dielectric ceramics of thickness (0.2 mm), electrode area (4 mm2) and operation voltage (2 kV). We report the pulse discharge performance parameters of three typical dielectric materials: relaxor ferroelectric (Na0.5Bi0.5)0.9Li0.1Ti0.9Ta0.1O3 (NBLTT), paraelectric Ca0.6-Sr0.4TiO3 (CST) and linear dielectric K0.5Na0.5NbO3 (KNN) glass ceramics through computer simulation and fitting of pulse discharge curves based on the resistance-inductance-capacitor pulse discharge circuit. The NBLTT ceramics exhibited higher peak current (16 A under 100 kV/cm) and stability with minimal variation less than 15% from 20 to 150 �C during pulse discharge compared with linear dielectric and ferroelectric glass ceramics. In addition, the NBLTT system holds the fast discharge time (90% of the discharge energy density released in about 100 ns) and good fatigue resistance. The short discharge time, high thermal stability and low medium voltage (500–5000 V) make the NBLTT ceramics promising for pulse capacitor in large current and low electric operation voltage conditions. An operable comparison standard and the research frontiers of pulsed dielectric materials are prospected

High Energy Storage Density and Optical Transparency of Microwave Sintered Homogeneous (Na_0.5Bi_0.5)_{(1–<i>x</i>)}­Ba_<i>x</i>Ti_{(1–<i>y</i>)}­Sn_<i>y</i>O₃ Ceramics

Homogeneous (Na_0.5Bi_0.5)_{(1–<i>x</i>)}­Ba_<i>x</i>Ti_{(1–<i>y</i>)}­Sn_<i>y</i>O₃ ceramics were densified by a combination of cold isostatic pressing and microwave sintering (CIP&MS strategy), and their phase transition and ferroelectric properties were investigated. X-ray diffraction (XRD) analysis proves that the reaction between Na_0.5Bi_0.5TiO₃ (NBT) and BaSnO₃ (BSN) was suppressed by fast sintering when <i>x</i> < 0.3. The grain size of the homogeneous ceramic sample was about 1 μm, and the uniform element distribution was detected by EDS mapping when <i>x</i> < 0.3. The <i>x</i> = 0.2 sample possesses a modest dielectric constant (∼2000), low dielectric loss (tan δ < 0.015), and highly diffusive and dispersive relaxor-like behavior. The weakly polar phase gradually increases and the energy loss gradually decreases with BSN addition. When <i>x</i> = 0.2, a high transparency in the visible spectra (∼50%) and the high discharge energy density (<i>W</i>_D) of 2.347 J/cm³ were achieved as a result of high homogeneous sample, meanwhile <i>P</i>_m was as high as 35.75 μC/cm². Then, a homogenization model was utilized to explain the high energy storage properties

Structural Evolution and Enhanced Piezoelectric Activity in Novel Lead-Free BaTiO3-Ca(Sn1/2Zr1/2)O3 Solid Solutions

In this study, a series of solid solutions of (1&minus;x)BaTiO3-xCa(Sn1/2Zr1/2)O3 (abbreviated as (1&minus;x)BT-xCSZ, x = 0.00&ndash;0.15) ceramics have been prepared by the conventional solid-state reaction method to search for high performance lead-free piezoelectric materials. The structural evolution, microstructure, and piezoelectric properties are investigated. X-ray diffraction (XRD) results indicate that the phase symmetry strongly depends on the CSZ content. A tetragonal phase is well-maintained in the compositions of 0 &le; x &le; 0.03, and coexistence of tetragonal and cubic phases is obtained in the range of x = 0.06&ndash;0.09, beyond which a pure cubic phase becomes stable. More importantly, a significantly enhanced piezoelectric coefficient of d33 = 388 &plusmn; 9 pC/N is attained in the composition of x = 0.06 in the MPB region, where a tetragonal ferroelectric phase and an ergodic relaxor phase with average cubic symmetry coexist. Based on the analysis of crystal structure and dielectric properties, a temperature-composition phase diagram consisting of four phase regions is established. This study indicates that the lead-free BT-CSZ binary system has great potential for use in electromechanical transducer applications

Structural Evolution and Enhanced Piezoelectric Activity in Novel Lead-Free BaTiO₃-Ca(Sn_1/2Zr_1/2)O₃ Solid Solutions

In this study, a series of solid solutions of (1−x)BaTiO3-xCa(Sn1/2Zr1/2)O3 (abbreviated as (1−x)BT-xCSZ, x = 0.00–0.15) ceramics have been prepared by the conventional solid-state reaction method to search for high performance lead-free piezoelectric materials. The structural evolution, microstructure, and piezoelectric properties are investigated. X-ray diffraction (XRD) results indicate that the phase symmetry strongly depends on the CSZ content. A tetragonal phase is well-maintained in the compositions of 0 ≤ x ≤ 0.03, and coexistence of tetragonal and cubic phases is obtained in the range of x = 0.06–0.09, beyond which a pure cubic phase becomes stable. More importantly, a significantly enhanced piezoelectric coefficient of d33 = 388 ± 9 pC/N is attained in the composition of x = 0.06 in the MPB region, where a tetragonal ferroelectric phase and an ergodic relaxor phase with average cubic symmetry coexist. Based on the analysis of crystal structure and dielectric properties, a temperature-composition phase diagram consisting of four phase regions is established. This study indicates that the lead-free BT-CSZ binary system has great potential for use in electromechanical transducer applications

Residual Sediment Transport in the Fine-Grained Jiangsu Coast under Changing Climate: The Role of Wind-Driven Currents

Residual sediment transport, which is influenced by many factors including tide, wind, and waves, controls coastal morphological changes on different time scales. For fine-grained coasts where the wave effects are limited, it is still unclear to what extent the wind-driven current can impact the residual sediment transport. Taking the fine-grained Jiangsu Coast as an example, this study aimed to identify the contribution of wind on residual sediment transport over different time scales using a newly developed model. On a seasonal scale, wind-induced sediment transport shows strong seasonal characteristics, where the residual transport is more significant in the winter and summer. Nevertheless, the tide plays a dominant role in both residual current and sediment transport and the annual sediment budget over the coast. On the scale of tidal cycles, the extreme winds overwhelm the tides, controlling the residual sediment transport. However, the net sediment transport caused by the northerly winds (representing cold waves) is comparable to that of the southerly winds (representing typhoons). Therefore, although extreme winds can drive massive sediment transport in a short period, their contribution to annual sediment transport is limited