Further Enhancing Piezoelectric Properties by Adding MnO2 in AgSbO3‐Modified (Li,K,Na)(Nb,Ta)O3 Lead‐Free Piezoceramics

This work investigated the effect of MnO₂ addition on the phase structure, microstructure, and electrical properties of AgSbO₃‐modified (Li,K,Na)(Nb,Ta)O₃ (abbreviated as LKNNT‐AS) lead‐free piezoelectric ceramics with an optimized composition endowed with a state of two‐phase coexistence. A small amount (0.1 wt%) of MnO₂ can significantly further enhance the piezoelectric property of LKNNT‐AS ceramics, whose piezoelectric constant d₃₃ and converse piezoelectric coefficient d₃₃* as well as planar electromechanical coupling factor k_p reach 363 pC/N, 543 pm/V, and 0.49, respectively. The temperature stability of piezoelectricity in MnO₂‐modified LKNNT‐AS samples also improved, which is associated with the more uniform and better thermally stable ferroelectric domains that were revealed by piezoresponse force microscopy.     

Large Piezoelectricity and Ferroelectricity in Mn‐Doped (Bi0.5Na0.5)TiO3‐BaTiO3 Thin Film Prepared by Pulsed Laser Deposition

Mn‐doped (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ (MnBNBT) thin films were prepared on SrRuO₃ (SRO)‐coated (001) SrTiO₃ (STO) single crystal substrates by pulsed laser deposition under different processing conditions. Structural characterization (i.e., XRD and TEM) confirms the epitaxial growth of STO/SRO/MnBNBT heterostructures. Through the judicious control of deposition temperature, the defect level within the films can be finely tuned. The MnBNBT thin film deposited at the optimized temperature exhibits superior ferroelectric and piezoelectric responses with remanent polarization P_r of 33.0 μC/cm² and piezoelectric coefficient d₃₃ of 120.0 ± 20 pm/V.     

Effect of ferroelectric polarization on piezo/photocatalysis in Ag nanoparticles loaded 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Zr0.1Ti0.9)O3 composites towards the degradation of organic pollutants

A 0.5(Ba_0.7Ca_0.3)TiO₃–0.5Ba(Zr_0.1Ti_0.9)O₃ (BCT-BZT) ceramic was studied for photocatalysis and piezocatalysis effects using dye degradation (methylene blue, rhodamine B, and methyl orange) and bacterial (Escherichia coli) disinfection from aqueous solution. To examine the effect of ferroelectric polarization, BCT-BZT powder was poled using the corona poling technique. Same time, BCT-BZT was converted into Ag/BCT-BZT composites as Ag induced surface plasmon resonance effect during photocatalysis. Piezocatalysis performance was assessed for dyes mineralization under ultrasonication. There was a significant impact of silver nanoparticles on the photo/piezocatalysis performance of BCT-BZT. Similarly, electric poling has also played a positive role in improving the photo/piezocatalysis in view of various dye degradation. These samples also showed effective antibacterial performance.     

Solar/visible light photocatalytic dye degradation using BaTi1−xFexO3 ceramics

BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2) were prepared via a solid-state reaction route. The presence of iron (Fe) in barium titanate (BaTiO₃) eventually decreased the energy bandgap; thus, its utilization for water cleaning application through photocatalysis process was explored (using methylene blue [MB] dye as an indicative pollutant in water). Characterization of the synthesized powder was performed through scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The bandgap of the synthesized powder was calculated as 3.2, 2.12, and 1.67 eV for BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2), respectively. BaTi_0.8Fe_0.2O₃ powder showed excellent results, and ∼71% of the MB dye (∼5 mg/L concentrated) was degraded using the photocatalysis process under visible light. To check the potentiality of BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2), the photocatalysis process was carried out by changing the concentration of MB dye (2.5–10 mg/L with a step of 2.5 mg/L) and the amount of BaTi_0.8Fe_0.2O₃ powder (0.05–0.2 g with a step of 0.05 g) for ∼5-mg/L concentrated MB dye. The treated water was further used as a growth parameter and phytotoxicity analysis through germination index on the wheat seeds. Lastly, the BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2) were explored for water cleaning applications under real-time solar irradiation.     

Large pyroelectricity via engineered ferroelectric-relaxor phase boundary

With growing demand for high-sensitivity infrared detectors in industrial temperature monitoring and medical systems, high-performance pyroelectric materials are vitally required. In this work, large pyroelectric performance is achieved in (1 − x)Pb_0.99Nb_0.02[(Zr_0.57Sn_0.43)_0.937Ti_0.063]_0.98O₃–xBaTiO₃ (1 − x)PNZST–xBT ceramics by tuning the ferroelectric (FE)-relaxor phase boundary near room temperature. The FE- and ergodic-relaxor phase boundaries are engineered by breaking the long-range antiferroelectric order with the introduction of BaTiO₃. It is found that the ceramics with x = 0.15 exhibit a large pyroelectric coefficient of 11.3 × 10^–4 C m^–2 K^–1 and figures of merit of F_i = 20.1 × 10^–10 m V^–1, F_v = 3.44 × 10^–2 m² C^–1, and F_d = 3.87 × 10^–5 Pa^–1/2 around room temperature due to engineered phase boundary. Our results provide the potential technological application for ultrasensitive infrared detector and scientific insights into pyroelectric ceramic design.     

La2O3掺杂SiO2-B2O3-Nb2O5复相微晶玻璃相界及储能性能研究

采用可控析晶法制备了La₂O₃掺杂的SiO₂-B₂O₃-Nb₂O₅ (SBN)复相微晶玻璃,利用DSC、Raman、XRD、SEM、铁电和介电性能测试等分析表征了La₂O₃掺杂对SBN复相微晶玻璃结构与储能性能的影响。结果表明:La₂O₃掺杂能够有效提高复相微晶玻璃的热稳定性,随着La₂O₃含量增加,系统析晶势垒增大,热膨胀系数先降低后升高,价键振动加剧,介电常数先增大后减小,介电损耗先减小后增大;掺杂1.00%(摩尔分数)La₂O₃时,复相微晶玻璃在40 kV/cm电场下的储能密度和储能效率最大,分别为0.031 J·cm^-3和77.6%;储能性能主要通过介电常数和击穿场强的协同作用来评价,La₂O₃能通过提高结构热稳定性和降低介电损耗来提高介电常数,当其引入体系后处于玻璃网络的空隙中,可有效增强材料耐击穿性能;复相微晶玻璃结构可以增加结构无序度,从而降低弛豫损耗,有效提高材料的储能性能。     

Electroactive phases of poly(vinylidene fluoride): Determination,processing and applications

Poly(vinylidene fluoride), PVDF, and its copolymers are the family of polymers with the highest dielectric constant and electroactive response, including piezoelectric, pyroelectric and ferroelectric effects. The electroactive properties are increasingly important in a wide range of applications such as in biomedicine, energy generation and storage, monitoring and control, and include the development of sensors and actuators, separator and filtration membranes and smart scaffolds, among others. For many of these applications the polymer should be in one of its electroactive phases. This review presents the developments and summarizes the main characteristics of the electroactive phases of PVDF and copolymers, indicates the different processing strategies as well as the way in which the phase content is identified and quantified. Additionally, recent advances in the development of electroactive composites allowing novel effects, such as magnetoelectric responses, and opening new applications areas are presented. Finally, some of the more interesting potential applications and processing challenges are discussed.     

First-principles study for surface tension and depolarizing effect on ferroelectric properties of BaTiO3 nanowires

The spontaneous polarization in ferroelectric (FE) nanowires (NWs) can be considerably enhanced due to the nanosize confinement by the first-principles calculations. The spontaneous polarization in a fully-relaxed BaTiO₃ NW with 2.0 nm in diameter is 1.18 times higher than that of bulk counterpart. The ferroelectric properties of the wire are found to generally depend on its dimensions through effects of the surface tension and near-surface depolarizing effect. The surface tension seems to be crucial for the giant enhancement of spontaneous polarization.     

Electrostrictive properties of ceramics obtained on the basis of ferroelectrk relaxors

We present the results for search of the best ceramic materials for electrostrictive transducers. We performed the following investigations: (1) investigation of different types of ferroelectric, antiferroelectric and non-polar complex oxides with perovskite (OPS) and tetragonal tungsten bronze (TBS) structures; (2) the investigations of the OPS with different degrees of the cations ordering; (3) the measurements of the electrostrictive coefficient Q, Curie-Weiss constant C_W, coefficient of linear thermal expansion λ, polarization P and dielectric permittivity ^σ_r; (4) the X-ray analysis of the structure. The electrostrictive deformation may be very high and the relative strain can be of the order 10^-3 in such materials.     

Fabrication and Characterization of Gate-Connected 1T2C-Type Ferroelectric Memory with Paired Bi4 − xLaxTi3O12 Capacitors

A gate-connected 1T2C-type ferroelectric memory, in which the bottom electrodes of paired ferroelectric capacitors are connected to the gate electrode of an underlying FET (field effect transistor) on the field oxide region, was fabricated using a Bi_{4 ? x}La_xTi₃O₁₂ (BLT) film and its electrical properties were characterized. The I_D-V_G (drain current-gate voltage) characteristics of a FET combined with a single ferroelectric capacitor showed that the paired capacitors had almost the same ferroelectric property. It was found in the readout operation that there existed an optimum voltage to maximize the drain current on/off ratio between datum ‘1’ and datum ‘0,’ and that the maximum ratio was as large as 6 × 10⁴. It was also found that the drain current level remained constant, even if the readout operation was repeatedly conducted. It was concluded from these results that the 1T2C-type memory was successfully fabricated using the proposed process and operated properly.