Estimation of gradient size of interfacial strain and its optimization for effective magnetoelectric coupling in (CoFe2O4) – (0.93Na0.5Bi0.5TiO3 – 0.07BaTiO3), 2-2 nano-composites

Strain-mediated coupling between the magnetic and electrically ordered phases plays a significant role in magnetoelectric (ME) nano-composites. This study explores a method to analyse and quantify interfacial strain using a grazing angle scan (α) in a ME composite optimised for a specific microstructure. The details of strain around the interface CoFe₂O₄ (CFO) – 0.93Na_0.5Bi_0.5TiO₃ – 0.07BaTiO₃ (NBT-BT) was determined by performing ‘α’ scan, in order to gather information at various depths of the NBT-BT layer around maximum intensity (110) reflection. The strain around the interface was observed to dominate over a spatial region of ～20–30 nm away from the interface. The Piezoresponse force microscopy (PFM) studies performed near the interface reveal that the strain constrain experienced by the ferroelectric layer operates such that polarisation rotation and domain wall motion are constrained compared to the strain relaxed region of the film. For effective strain transfer, heterostructures grown with optimised thicknesses (～20–30 nm) exhibited a superior inverse piezomagnetic effect.     

Dielectric, Ferroelectric and Piezoelectric Studies of PMN Modified PLZT Ceramics

Dielectric, ferroelectric and piezoelectric properties of xPb(Mg_1/3Nb_2/3)O₃-(1-x)(Pb_0.988 La_0.012)(Zr_0.535Ti_0.465)O₃ ceramic system synthesized through columbite precursor method are investigated. X-ray diffraction patterns of ceramics indicated pseudocubic phase formation with pyrochlore phase. Grain growth (4.47 μ m) and apparent density (7.68 gm/cm³) enhanced remarkably in 0.8PMN-0.2PLZT composition, respectively. Increasing PMN content remarkably increased both room temperature dielectric permittivity (ε_RT = 2316) and dielectric maximum (ε_Tc = 24747) in 0.6PMN-0.4PLZT composition, respectively. PMN substitution in PLZT system enhanced the ferroelectric remanent (P_r = 28.4 μ C/cm²) and spontaneous (P_s = 31.2 μ C/cm²) polarization while coercive field (E_c) continuously decreased in xPMN-(1-x)PLZT system. PMN modification in PLZT system influenced piezoelectric properties (d₃₃, k_p and k_t) throughout the PMN-PLZT system.     

压电智能夹层及其特性分析

压电智能夹层可以有效地解决压电自诊断系统中直接使用压电片引起的弊端.通过适当改进当前的柔性印刷线路工艺制作出的压电智能夹层,不仅具有柔性印刷线路的特点,而且,应用在结构健康监测系统中还有其他一些独特的优越性能.并利用压电智能夹层进行了初步的拉伸载荷识别,同压电片相比,识别效果更明显.     

压电复合材料设计专家系统的原型设计

建立了一个压电复合材料设计专家系统的原型，原型系统由一个采用了不精确推理和元控制推理技术的推理机，三个材料知识库，两个元知识库以及辅助性功能模块组成，能够模拟材料设计专家，为水声换能器所需的压电复合材料提出设计方案，经过用户使用过程中对其知识库的不断完善，最终可在室运用计算机进行材料设计的实用目的。     

Sub-microsecond X-ray crystallography: techniques,challenges, and applications for materials science

Dynamics of crystals is a subject of recent interest in solid-state physics and a challenge for modern X-ray crystallography. Time-dependent response of solids to an external perturbation on atomic and microstructural length scales is the key to understanding many physical properties. This paper reviews the challenges and opportunities for probing of sub-micro-, micro-, and millisecond dynamics of solids using the methods of X-ray crystallography. It starts with an overview of recent time-resolved X-ray diffraction techniques. It then focuses on the processes that are important for understanding functional materials: dynamics of ferroelectric and ferroelastic domain patterns, texture in piezoelectric ceramics, mechanical resonances in solids, and dynamics of structural disorder. Knowledge available from macroscopic experiments is summarized, and opportunities for X-ray crystallography to resolve existing controversies are presented. This paper suggests the possible synergy of macroscopic and X-ray crystallographic experimental techniques.     

Flexible Piezoelectric Acoustic Sensors and Machine Learning for Speech Processing

Flexible piezoelectric acoustic sensors have been developed to generate multiple sound signals with high sensitivity, shifting the paradigm of future voice technologies. Speech recognition based on advanced acoustic sensors and optimized machine learning software will play an innovative interface for artificial intelligence (AI) services. Collaboration and novel approaches between both smart sensors and speech algorithms should be attempted to realize a hyperconnected society, which can offer personalized services such as biometric authentication, AI secretaries, and home appliances. Here, representative developments in speech recognition are reviewed in terms of flexible piezoelectric materials, self-powered sensors, machine learning algorithms, and speaker recognition.     

Cold sintering of the ceramic potassium sodium niobate, (K0.5Na0.5)NbO3, and influences on piezoelectric properties

Cold Sintering was applied to densify a Potassium-Sodium Niobate solid solution composition, 0.5KNbO₃-0.5NaNbO₃ (KNN); the process uses a transient chemical sintering aid, moderate pressure (400 MPa), and temperatures between 230–300 °C to obtain ceramics of ～92 to 96 % theoretical density. Typically, sintering temperatures between ～1000?1050 °C are required to density KNN using conventional methods. In this paper, the densification was investigated during heating, particularly the shrinkage in the first 60 min of the cold sintering process. The low-field dielectric and electrical properties of the resulting ceramics were found to be comparable to conventionally sintered KNN. Electric fields up to 80 kV/cm could be applied, however the ceramics showed pinched hysteresis loops, even after poling over a wide range of temperatures and electric fields. A Rayleigh analysis was used to investigate domain dynamics and high reversible permittivity. The irreversible behavior was an order of magnitude lower than in conventionally sintered KNN, likely associated with defect pinning of ferroelectric domains. A Transmission Electron Microscopy (TEM) study revealed a high density of line defects in most grains; dislocations in the grains limit poling and domain wall movement, thus suppressing both the piezoelectric properties and the hysteresis. Furthermore, TEM observations indicated crystalline grain boundaries that were faceted with terrace kink ledges. These observations point to the importance of the initial powder optimization and grain boundary diffusion when using cold sintering to prepare ceramics that are intended to show bulk cooperative properties such as ferroelectricity. The impact of limited high temperature homogenization of bulk diffusional processes is discussed.     

Evolution of structure and electrical properties with lanthanum content in [(Bi1/2Na1/2)0.95Ba0.05]1−xLaxTiO3 ceramics

Lead-free perovskite [(Bi_1/2Na_1/2)_0.95Ba_0.05]_1−xLa_xTiO₃ (x = 0.00–0.10) ceramics were fabricated via the solid state reaction method and their crystal structures and electrical properties were systematically studied. Transmission electron microscopy examination reveals a transition from a rhombohedral R3c phase with micron-sized complex domains to a mixture of rhombohedral R3c and tetragonal P4bm phases with nanodomains as La content was increased. X-ray diffraction analysis on bulk samples, however, indicates a pseudocubic structure in La-doped compositions. Electrical poling seems to transform the pseudocubic structure to a rhombohedral phase in compositions with 0.00 < x < 0.03. With La addition, the depolarization temperature (T_d) is observed to decrease and the dielectric constant (ɛ_r) within 100–350 °C becomes more temperature independent, promising for applications in high-temperature capacitors. Electric field-induced polarizations and strains display complex changes with respect to La concentration, with the highest strain of 0.35% achieved in the composition x = 0.04 under 70 kV/cm at room temperature. The piezoelectric coefficient d₃₃ initially increases with La content, reaching a maximum value of 151 pC/N in the composition x = 0.02, and then diminishes.